UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

For the Fiscal Year Ended December 31, 2004

Commission file No. 000-32837

UNITED SURGICAL PARTNERS INTERNATIONAL, INC.

(Exact name of Registrant as specified in its charter)

(972) 713-3500

(Registrant’s telephone number, including area code)

Securities Registered Pursuant to Section 12(b) of the Act:

None

Securities Registered Pursuant to Section 12(g) of the Act:

      Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.     Yes þ          No o

      Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of Registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Parts I, II, III, and IV of this Form 10-K or any amendment to this Form 10-K.     o

      Indicate by check mark whether the registrant is an accelerated filer (as defined in Exchange Act Rule 12b-2).     Yes þ          No o

DOCUMENTS INCORPORATED BY REFERENCE

      Part III — Portions of the registrant’s definitive proxy statement to be filed pursuant to Regulation 14A for the Annual Meeting of Stockholders to be held May 3, 2005.

UNITED SURGICAL PARTNERS INTERNATIONAL, INC.

2004 ANNUAL REPORT ON FORM 10-K

TABLE OF CONTENTS

FORWARD LOOKING STATEMENTS

      Certain statements contained in this Annual Report on Form 10-K, and the document incorporated herein by reference, including, without limitation, statements containing the words “believes”, “anticipates”, “expects”, “continues”, “will”, “may”, “should”, “estimates”, “intends”, “plans” and similar expressions, and statements regarding the Company’s business strategy and plans, constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Such forward-looking statements are based on management’s current expectations and involve known and unknown risks, uncertainties and other factors, many of which the Company is unable to predict or control, that may cause the Company’s actual results, performance or achievements to be materially different from those expressed or implied by such forward-looking statements. Such factors include, among others, the following: general economic and business conditions, both nationally and regionally; foreign currency fluctuations; demographic changes; changes in, or the failure to comply with, laws and governmental regulations; the ability to enter into and retain managed care provider arrangements on acceptable terms; changes in Medicare, Medicaid and other government funded payments or reimbursement in the U.S. and the United Kingdom; liability and other claims asserted

against us; the highly competitive nature of healthcare; changes in business strategy or development plans of healthcare systems with which we partner; the ability to attract and retain qualified physicians, nurses, other health care professionals and other personnel; our significant indebtedness; the availability of suitable acquisition and development opportunities and the length of time it takes to accomplish acquisitions and developments; our ability to integrate new businesses with our existing operations; the availability and terms of capital to fund the expansion of our business, including the acquisition and development of additional facilities and certain additional factors, risks and uncertainties discussed in this Annual Report on Form 10-K and the document incorporated herein by reference. Given these uncertainties, investors and prospective investors are cautioned not to rely on such forward-looking statements. We disclaim any obligation and make no promise to update any such factors or forward-looking statements or to publicly announce the results of any revisions to any such factors or forward-looking statements, whether as a result of changes in underlying factors, to reflect new information as a result of the occurrence of events or developments or otherwise.

PART I

General

      United Surgical Partners International, Inc. (together with its subsidiaries, “we”, the “Company” or “USPI”) owns and operates short stay surgical facilities including surgery centers and private surgical hospitals in the United States and the United Kingdom. We focus on providing high quality surgical facilities that meet the needs of patients, physicians and payors better than hospital-based and other outpatient surgical facilities. We believe that our facilities (1) enhance the quality of care and the healthcare experience of patients, (2) offer significant administrative, clinical and economic benefits to physicians, (3) offer a strategic approach for our health system partners to expand capacity and access within the markets they serve and (4) offer an efficient and low cost alternative to payors. We acquire and develop our facilities through the formation of strategic relationships with physicians and healthcare systems to better access and serve the communities in our markets. Our operating model is efficient, scalable and portable and we have adapted it to each of our markets. We believe that our acquisition and development strategy and operating model enable us to continue to grow by taking advantage of highly-fragmented markets and an increasing demand for short stay surgery.

      Since physicians provide and influence the direction of healthcare in the U.S. and U.K., we have developed our operating model to encourage physicians to affiliate with us and to use our facilities as an extension of their practices. We operate our facilities, structure our strategic relationships and adopt staffing, scheduling and clinical systems and protocols with the goal of increasing physician productivity. We believe that our focus on physician satisfaction, combined with providing high quality healthcare in a friendly and convenient environment for patients, will continue to increase the number of procedures performed at our facilities each year.

      Donald E. Steen, our chairman, and Welsh, Carson, Anderson & Stowe formed USPI in February 1998. We operate surgery centers and private surgical hospitals in the United States and the United Kingdom. As of December 31, 2004, we operated 87 facilities, consisting of 84 in the United States and three in the United Kingdom. Of the 84 U.S. facilities, 48 are jointly owned with major not-for-profit healthcare systems. Overall, as of December 31, 2004, we held ownership interests in 85 of the facilities and operated the remaining two facilities under management or service contracts. Our revenues for 2004 were $389.5 million, up 25% from $310.6 million for 2003.

Available Information

      We file proxy statements and annual, quarterly and current reports with the Securities and Exchange Commission. You may read and copy any document that we file at the SEC’s public reference room located at 450 Fifth Street N.W., Washington, D.C. 20549. You may also call the Securities and Exchange Commission at 1-800-SEC-0330 for information on the operation of the public reference room. Our SEC filings are also available to you free of charge at the SEC’s web site at http://www.sec.gov. We also maintain a web site at http://www.unitedsurgical.com that includes links to our annual reports on Form  10-K, quarterly reports on Form 10-Q, current reports on Form 8-K and any amendments to those reports. These reports are available on our website without charge as soon as reasonably practicable after such reports are filed with or furnished to the SEC. We post our audit and compliance committee, options and compensation committee, and nominating and corporate governance committee charters, our corporate governance guidelines, and our financial code of ethics applicable to senior financial officers on our web site. These documents are available free of charge to any stockholder upon request. Information on our web site is not deemed incorporated by reference into this Form 10-K.

Industry Background

      We believe many physicians prefer surgery centers and private surgical hospitals to general acute care hospitals. We believe that this is due to the elective nature of the procedures performed at our surgery centers

and private surgical hospitals, which allows physicians to schedule their time more efficiently and therefore increase the number of surgeries they can perform in a given amount of time. In addition, these facilities usually provide physicians with greater scheduling flexibility, more consistent nurse staffing and faster turnaround time between cases. While surgery centers and private surgical hospitals generally perform scheduled surgeries, private acute care hospitals and national health service facilities generally provide a broad range of services, including high priority and emergency procedures. Medical emergencies often demand the unplanned use of operating rooms and result in the postponement or delay of scheduled surgeries, disrupting physicians’ practices and inconveniencing patients. Surgery centers and private surgical hospitals in the United States and the United Kingdom are designed to improve physician work environments and improve physician efficiency. In addition, many physicians choose to perform surgery in facilities like ours because their patients prefer the comfort of a less institutional atmosphere and the convenience of simplified admissions and discharge procedures.

      According to Verispan’s 2004 Outpatient Surgery Center Market Report, the number of outpatient surgery cases performed in freestanding surgery centers increased 93% from 4.3 million in 1996 to an estimated 8.3 million in 2004. New surgical techniques and technology, as well as advances in anesthesia, have significantly expanded the types of surgical procedures that are being performed in surgery centers and have helped drive the growth in outpatient surgery. Lasers, arthroscopy, enhanced endoscopic techniques and fiber optics have reduced the trauma and recovery time associated with many surgical procedures. Improved anesthesia has shortened recovery time by minimizing post-operative side effects such as nausea and drowsiness, thereby avoiding the need for overnight hospitalization in many cases. In addition, some states in the United States now permit surgery centers to keep a patient for up to 23 hours. This allows more complex surgeries, previously only performed in an inpatient setting, to be performed in a surgery center.

      In addition to these technological and other clinical advancements, a changing payor environment has contributed to the rapid growth in outpatient surgery in recent years. Government programs, private insurance companies, managed care organizations and self-insured employers have implemented cost containment measures to limit increases in healthcare expenditures, including procedure reimbursement. These cost containment measures have contributed to the significant shift in the delivery of healthcare services away from traditional inpatient hospitals to more cost-effective alternate sites, including surgery centers. We believe that surgery performed at a surgery center is generally less expensive than hospital-based outpatient surgery because of lower facility development costs, more efficient staffing and space utilization and a specialized operating environment focused on cost containment.

      Today, large healthcare systems in the United States generally offer both inpatient and outpatient surgery on site. In addition, a number of not-for-profit healthcare systems have begun to expand their portfolios of facilities and services by entering into strategic relationships with specialty operators of surgery centers in order to expand capacity and access in the markets they serve. These strategic relationships enable not-for-profit healthcare systems to offer patients, physicians and payors the cost advantages, convenience and other benefits of outpatient surgery in a freestanding facility. Further, these relationships allow the not-for-profit healthcare systems to focus their attention and resources on their core business without the challenge of acquiring, developing and operating these facilities.

      The United Kingdom provides government-funded healthcare to all of its residents through a national health service. However, due to funding and capacity limitations, the demand for healthcare services exceeds the public system’s capacity, resulting in waiting lists for elective surgery of up to 18 months as well as delays in obtaining cancer biopsies and other diagnostic procedures. In response to these shortfalls, private healthcare networks and private insurance companies have developed in the United Kingdom. Approximately 11% of the U.K. population has private insurance to cover elective surgical procedures, and another rapidly growing segment of the population pays for elective procedures from personal funds. For the year ended December 31, 2004, in the United Kingdom, we derived approximately 50% of our revenues from private insurance,

approximately 43% from self-pay patients, who typically arrange for payment prior to surgery being performed, and approximately 7% from government payors.

Our Business Strategy

      Our goal is to steadily increase our revenues and cash flows by becoming a leading operator of surgery centers and private surgical hospitals in the United States and the United Kingdom. The key elements of our business strategy are to:

      Since physicians provide and influence the direction of healthcare in the U.S. and U.K., we have developed our operating model to encourage physicians to affiliate with us and to use our facilities as an extension of their practices. We believe we attract physicians because we design our facilities, structure our strategic relationships and adopt staffing, scheduling and clinical systems and protocols to increase physician productivity and promote their professional and financial success. We believe this focus on physicians, combined with providing high quality healthcare in a friendly and convenient environment for patients, will continue to increase case volumes at our facilities. In addition, in the United States, we generally offer physicians the opportunity to purchase equity interests in the facilities they use as an extension of the physicians’ practices. We believe this opportunity attracts quality physicians to our facilities and ownership increases the physicians’ involvement in facility operations, enhancing quality of patient care, increasing productivity and reducing costs.

      Through strategic relationships with us, not-for-profit healthcare systems can benefit from our operating expertise and create a new cash flow opportunity with limited capital expenditures. We believe that these relationships also allow not-for-profit healthcare systems to attract and retain physicians and improve their hospital operations by focusing on their core business. We also believe that strategic relationships with these healthcare systems help us to more quickly develop relationships with physicians, communities, and payors. Generally, the healthcare systems with which we develop relationships have strong local market positions and excellent reputations that we use in branding our facilities. In addition, our relationships with not-for-profit healthcare systems enhance our acquisition and development efforts by (1) providing opportunities to acquire facilities the systems may own, (2) providing access to physicians already affiliated with the systems, (3) attracting additional physicians to affiliate with newly developed facilities, and (4) encouraging physicians who own facilities to consider a strategic relationship with us.

      Our primary strategy is to grow selectively in markets in which we already operate facilities. We believe that selective acquisitions and development of new facilities in existing markets allow us to leverage our existing knowledge of these markets and to improve operating efficiencies. In particular, our experience has been that newly developed facilities in markets where we already have a presence and a not-for-profit hospital partner are the best use of the company’s invested capital.

      We may continue to enter targeted markets by acquiring and developing surgical facilities. In the United States, we expect to do this primarily in conjunction with a local healthcare system or hospital. We typically target the acquisition or development of multi-specialty centers that perform high volume, non-emergency, lower risk procedures requiring lower capital and operating costs than hospitals. In addition, we will also consider the acquisition of multi-facility companies.

      In determining whether to enter a new market, we examine numerous criteria, including:

      Upon identifying a target facility, we conduct financial, legal and compliance, operational, technology and systems reviews of the facility and conduct interviews with the facility’s management, affiliated physicians and staff. Once we acquire or develop a facility, we focus on upgrading systems and protocols, including implementing our proprietary methodology of defined processes and information systems, to increase case volume and improve operating efficiencies.

      Once we acquire a new facility in the U.S., we integrate it into our existing network by implementing a specific action plan to support the local management team and incorporate the new facility into our group purchasing contracts. We also implement our systems and protocols to improve operating efficiencies and contain costs. Our most important operational tool is our management system “Every Day Giving Excellence,” which we refer to as USPI’s EDGE. This proprietary measurement system allows us to track our clinical, service and financial performance, best practices and key indicators in each of our facilities. Our goal is to use USPI’s EDGE to ensure that we provide each of the patients using our facilities with high quality healthcare, offer physicians a superior work environment and eliminate inefficiencies. Using USPI’s EDGE, we track and monitor our performance in areas such as (1) providing surgeons the equipment, supplies and surgical support they need, (2) starting cases on time, (3) minimizing turnover time between cases, and (4) providing efficient schedules. USPI’s EDGE compiles and organizes the specified information on a daily basis and is easily accessed over the Internet by our facilities on a secure basis. The information provided by USPI’s EDGE enables our employees, facility administrators and management to analyze trends over time and share processes and best practices among our facilities. In addition, the information is used as an evaluative tool by our administrators and as a budgeting and planning tool by our management. USPI’s EDGE is now deployed in all but our most recently acquired U.S. facilities.

Operations

      Our operations in the United States consist primarily of our ownership and management of surgery centers. We have ownership interests in 73 surgery centers and nine private surgical hospitals and manage or operate, through agreements, two additional surgery centers. Additionally, we own interests in and expect to operate five surgery centers and one private surgical hospital that are currently under construction. We also have eleven projects under development, all of which include a hospital partner, and numerous other potential

projects in various stages of consideration, which may result in our adding additional facilities during 2005. Over 3,600 physicians have privileges to use our facilities. Our surgery centers are licensed outpatient surgery centers; our private surgical hospitals are licensed as hospitals. Both are generally equipped and staffed for multiple surgical specialties and located in freestanding buildings or medical office buildings. Our average surgery center has approximately 12,000 square feet of space with four operating rooms, as well as ancillary areas for preparation, recovery, reception and administration. Our surgery center facilities range from a 4,000 square foot, one operating room facility to a 33,000 square foot, nine operating room facility. Our surgery centers are normally open weekdays from 7:00 a.m. to approximately 5:00 p.m. or until the last patient is discharged. We estimate that a surgery center with four operating rooms can accommodate up to 6,000 procedures per year. Our surgical hospitals average 40,000 square feet of space with six operating rooms, ranging in size from 17,000 to 68,000 square feet and having from 4 to 8 operating rooms.

      Our surgery center support staff typically consists of registered nurses, operating room technicians, an administrator who supervises the day-to-day activities of the surgery center, and a small number of office staff. Each center also has a medical director, who is responsible for and supervises the quality of medical care provided at the center. Use of our surgery centers is generally limited to licensed physicians, podiatrists and oral surgeons who are also on the medical staff of a local accredited hospital. Each center maintains a peer review committee consisting of physicians who use our facilities and who review the professional credentials of physicians applying for surgical privileges.

      All but two of our surgical facilities are accredited by either the Joint Commission on Accreditation of Healthcare Organizations or by the Accreditation Association for Ambulatory Healthcare or are in the process of applying for such accreditation. We believe that accreditation is the quality benchmark for managed care organizations. Many managed care organizations will not contract with a facility until it is accredited. We believe that our historical performance in the accreditation process reflects our commitment to providing high quality care in our surgical facilities.

      Generally, our surgical facilities are limited partnerships, limited liability partnerships or limited liability companies in which ownership interests are also held by local physicians who are on the medical staff of the centers. Our ownership interests in the centers range from 7.5% to 95%. Our partnership and limited liability company agreements typically provide for the monthly or quarterly pro rata distribution of cash equal to net revenues from operations, less amounts held in reserve for expenses and working capital. Our facilities derive their operating cash flow by collecting a fee from patients, insurance companies, or other payors in exchange for providing the facility and related services a surgeon requires in order to perform a surgical case. Our billing systems estimate revenue and generate contractual adjustments based on a fee schedule for over 75% of the total cases performed at our facilities. For the remaining cases, the contractual allowance is estimated based on the historical collection percentages of each facility by payor group. The historical collection percentage is updated quarterly for each facility. We estimate each patient’s financial obligation prior to the date of service. We request payment of that obligation at the time of service. Any amounts not collected at the time of service are subject to our normal collection and reserve policy. We also have a management agreement with each of the facilities under which we provide day-to-day management services for a management fee that is typically a percentage of the net revenues of the facility.

      Our partnership and limited liability company agreements typically provide that if various regulatory changes take place we will be obligated to purchase some or all of the ownership interests of the physicians in the partnerships or limited liability companies that own and operate the applicable surgery centers. The regulatory changes that could trigger such an obligation include changes that:

      Typically, our partnership and limited liability company agreements allow us to use shares of our common stock as consideration for the purchase of a physician’s interest should we be required to purchase these interests. In the event we are required to purchase these interests and our common stock does not maintain a sufficient valuation, we may be required to use cash for the acquisition of a physician’s interest. As a result, the triggering of these obligations and the possible termination of our affiliation with these physicians, which we do not believe is likely, could have a material adverse effect on us.

      Our business depends upon the efforts and success of the physicians who provide medical services at our facilities and the strength of our relationships with these physicians. Our business could be adversely affected by the loss of our relationship with, or a reduction in use of our facilities by, a key physician or group of physicians. The physicians that affiliate with us and use our facilities are not our employees. However, we generally offer the physicians the opportunity to purchase equity interests in the facilities they use.

      A key element of our business strategy is to pursue strategic relationships with not-for-profit healthcare systems (“hospital partners”) in selected markets. Of our 84 U.S. facilities, 48 are jointly-owned with not-for-profit healthcare systems. Our strategy involves developing these relationships in three primary ways. One way is by adding new facilities in existing markets with our existing hospital partners. An example of this is our relationship with the Baylor Health Care System in Dallas, Texas. Our joint ventures with Baylor own a network of 20 operational surgical facilities that serve the approximately four million people in the Dallas/ Fort Worth area. These joint ventures have added new facilities each year since their inception in 1999, including three during 2004, and have an additional two facilities under construction.

      Another way we develop these relationships is through expansion into new markets, both with existing hospital partners and with new partners. An example of this strategy with an existing partner is our expansion into new markets with Catholic Healthcare West (CHW). Our relationship with CHW began in 1998 with a facility in Las Vegas, Nevada, expanded into Phoenix, Arizona with three facilities, two of which were newly developed, during 2003, and continues as we enter new markets in California, where we have two facilities under construction and an additional two under development, some of which we expect to open in 2005. Another example of this strategy is our relationship with Ascension Health, with whom we jointly own facilities in Nashville, Tennessee and with whom we entered the Baltimore, Maryland market through the acquisition of an equity interest in a facility during 2004. During 2004 we entered the Oklahoma market with a new partner, INTEGRIS Health, through the acquisition of equity interests in two facilities, and opened facilities with CHRISTUS Health in San Antonio, Texas, with Bon Secours Health System in Newport News, Virginia, and Providence Health System, in Mission Hills, California. We expect projects currently under development to result in our opening facilities in additional new markets with not-for-profit hospital partners.

      A third way we develop our strategic relationships with not-for-profit healthcare systems is through the contribution of our ownership interests in existing facilities to a joint venture relationship. During 2003 and 2004 we added a not-for-profit hospital partner to six facilities we had previously operated without a hospital partner. We expect to add a not-for-profit hospital partner in the future to some of the remaining 36 facilities that do not yet have such a partner.

      We operate three private hospitals in greater London. We acquired Parkside Hospital and Holly House Hospital in 2000 and Highgate Hospital in 2003. Parkside Hospital, located in Wimbledon, a suburb southwest of London, has 69 registered acute care beds, including four high dependency beds and four operating theatres, one of which is a dedicated endoscopy suite. Parkside also has its own on-site pathology laboratory which provides services to the on-site cancer treatment center. The imaging department, which has been extensively upgraded in the past three years, has an MRI scanner, CT scanner, and two X-ray screening rooms, plus mammography, dental and ultrasound services available. Approximately 415 surgeons, anesthesiologists, and physicians, all of whom have been subject to a strict credentialing process and continue to

participate in annual appraisal programs that Parkside shares with a local hospital operated by the United Kingdom’s national health service, have admitting privileges to the hospital. Parkside’s key specialties include orthopedics, oncology, gynecology, neurosurgery, ear-nose-throat, endoscopy and general surgery, and the hospital is currently expanding its day case services.

      Parkside Oncology Clinic opened in August 2003 and has state of the art equipment designed to provide a wide range of cancer treatments. The pre-treatment and planning suite houses a dedicated CT scanner, which, along with the linear accelerators and virtual simulation software, is linked to the department’s planning system. The clinic also has its own pharmacy aseptic suite which provides chemotherapy to the day case unit at the hospital.

      Holly House Hospital, located in a suburb northeast of London near Essex, has been an acute care hospital for over 20 years and has 55 registered acute care beds, including three high dependency beds. The hospital has three operating theatres and its own on-site pathology laboratory and pharmacy. A diagnostic suite houses MRI and CT scanners, X-ray screening rooms, mammography, ultrasound, and DEXA scanning as well as Kodak Computer Radiography. Over 260 surgeons, anesthesiologists, and physicians have admitting privileges at the hospital, and there are well-established orthopedic, plastic, IVF, and general surgery practices.

      Highgate Hospital is a 32 bed acute care hospital located in the affluent Highgate area of London. The hospital has an established cosmetic surgery business and additional practices including endoscopy and general surgery are being developed.

      The following table sets forth the percentage of our revenues determined based on internally reported case volume from our U.S. facilities and internally reported revenue from our U.K. facilities for the year ended December 31, 2004 from each of the following specialties:

      The following table sets forth the percentage of our revenues determined based on internally reported case volume from our U.S. surgical facilities and internally reported revenue from our U.K. facilities for the year ended December 31, 2004 from each of the following payors:

      The following table sets forth information relating to the not-for-profit healthcare systems with which we are affiliated as of December 31, 2004:

      The following table sets forth information relating to the facilities that we operated as of December 31, 2004: