UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

Commission File No. 0-16741

COMSTOCK RESOURCES, INC.

(Exact name of registrant as specified in its charter)

5300 Town and Country Blvd., Suite 500, Frisco, Texas 75034

(Address of principal executive offices including zip code)

(972) 668-8800

(Registrant’s telephone number and area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

      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 Part III of this Form 10-K.     þ

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

      The aggregate market value of the voting common equity held by non-affiliates of the Registrant computed by reference to the price at which the common equity was last sold as of the last business day of the Registrant’s most recently completed second fiscal quarter was $658.0 million.

      As of March 17, 2005, there were 36,037,868 shares of common stock outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

      Proxy statement for the 2005 annual meeting of stockholders — Part III

COMSTOCK RESOURCES, INC.

ANNUAL REPORT ON FORM 10-K

For the Fiscal Year Ended December 31, 2004

CONTENTS

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

      The information contained in this report includes “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. These forward-looking statements are identified by their use of terms such as “expect,” “estimate,” “anticipate,” “project,” “plan,” “intend,” “believe” and similar terms. All statements, other than statements of historical facts, included in this report, are forward-looking statements, including statements mentioned under “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” regarding:

      Any or all of our forward-looking statements in this report may turn out to be incorrect. They can be affected by a number of factors, including, among others:

DEFINITIONS

      The following are abbreviations and definitions of terms commonly used in the oil and gas industry and this report. Natural gas equivalents and crude oil equivalents are determined using the ratio of six Mcf to one barrel. All references to “us,” “our,” “we” or “Comstock” mean the registrant, Comstock Resources, Inc. and where applicable, its consolidated subsidiaries.

      Bbl means a barrel of 42 U.S. gallons of oil.

      Bcf means one billion cubic feet of natural gas.

      Bcfe means one billion cubic feet of natural gas equivalent.

      Btu means British thermal unit, which is the quantity of heat required to raise the temperature of one pound of water from 58.5 to 59.5 degrees Fahrenheit.

      Completion means the installation of permanent equipment for the production of oil or gas.

      Condensate means a hydrocarbon mixture that becomes liquid and separates from natural gas when the gas is produced and is similar to crude oil.

      Development well means a well drilled within the proved area of an oil or gas reservoir to the depth of a stratigraphic horizon known to be productive.

      Dry hole means a well found to be incapable of producing hydrocarbons in sufficient quantities such that proceeds from the sale of such production exceed production expenses and taxes.

      Exploratory well means a well drilled to find and produce oil or natural gas reserves not classified as proved, to find a new productive reservoir in a field previously found to be productive of oil or natural gas in another reservoir or to extend a known reservoir.

      Gross when used with respect to acres or wells, production or reserves refers to the total acres or wells in which we or another specified person has a working interest.

      MBbls means one thousand barrels of oil.

      MBbls/d means one thousand barrels of oil per day.

      Mcf means one thousand cubic feet of natural gas.

      Mcfe means thousand cubic feet of natural gas equivalent.

      MMBbls means one million barrels of oil.

      MMcf means one million cubic feet of natural gas.

      MMcf/d means one million cubic feet of natural gas per day.

      MMcfe/d means one million cubic feet of natural gas equivalent per day.

      MMcfe means one million cubic feet of natural gas equivalent.

      Net when used with respect to acres or wells, refers to gross acres of wells multiplied, in each case, by the percentage working interest owned by us.

      Net production means production we own less royalties and production due others.

      Oil means crude oil or condensate.

      Operator means the individual or company responsible for the exploration, development, and production of an oil or gas well or lease.

      PV 10 Value means the present value of estimated future revenues to be generated from the production of proved reserves calculated in accordance with the Securities and Exchange Commission guidelines, net of estimated production and future development costs, using prices and costs as of the date of estimation without

future escalation, without giving effect to non-property related expenses such as general and administrative expenses, debt service, future income tax expense and depreciation, depletion and amortization, and discounted using an annual discount rate of 10%. This amount is the same as the standardized measure of discounted future net cash flows related to proved oil and natural gas reserves except that it is determined without deducting future income taxes.

      Proved developed reserves means reserves that can be expected to be recovered through existing wells with existing equipment and operating methods. Additional oil and gas expected to be obtained through the application of fluid injection or other improved recovery techniques for supplementing the natural forces and mechanisms of primary recovery will be included as “proved developed reserves” only after testing by a pilot project or after the operation of an installed program has confirmed through production response that increased recovery will be achieved.

      Proved developed non-producing means reserves (i) expected to be recovered from zones capable of producing but which are shut-in because no market outlet exists at the present time or whose date of connection to a pipeline is uncertain or (ii) currently behind the pipe in existing wells, which are considered proved by virtue of successful testing or production of offsetting wells.

      Proved developed producing means reserves expected to be recovered from currently producing zones under continuation of present operating methods. This category may also include recently completed shut-in gas wells scheduled for connection to a pipeline in the near future.

      Proved reserves means the estimated quantities of crude oil, natural gas, and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions, i.e., prices and costs as of the date the estimate is made. Prices include consideration of changes in existing prices provided only by contractual arrangements, but not on escalations based upon future conditions.

      Proved undeveloped reserves means reserves that are expected to be recovered from new wells on undrilled acreage, or from existing wells where a relatively major expenditure is required for recompletion. Reserves on undrilled acreage shall be limited to those drilling units offsetting productive units that are reasonably certain of production when drilled. Proved reserves for other undrilled units can be claimed only where it can be demonstrated with certainty that there is continuity of production from the existing productive formation. Under no circumstances should estimates for proved undeveloped reserves be attributable to any acreage for which an application of fluid injection or other improved recovery technique is contemplated, unless such techniques have been proved effective by actual tests in the area and in the same reservoir.

      Recompletion means the completion for production of an existing well bore in another formation from which the well has been previously completed.

      Reserve life means the calculation derived by dividing year-end reserves by total production in that year.

      Reserve replacement means the calculation derived by dividing additions to reserves from acquisitions, extensions, discoveries and revisions of previous estimates in a year by total production in that year.

      Royalty means an interest in an oil and gas lease that gives the owner of the interest the right to receive a portion of the production from the leased acreage (or of the proceeds of the sale thereof), but generally does not require the owner to pay any portion of the costs of drilling or operating the wells on the leased acreage. Royalties may be either landowner’s royalties, which are reserved by the owner of the leased acreage at the time the lease is granted, or overriding royalties, which are usually reserved by an owner of the leasehold in connection with a transfer to a subsequent owner.

      3-D seismic means an advanced technology method of detecting accumulations of hydrocarbons identified by the collection and measurement of the intensity and timing of sound waves transmitted into the earth as they reflect back to the surface.

      Working interest means an interest in an oil and gas lease that gives the owner of the interest the right to drill for and produce oil and gas on the leased acreage and requires the owner to pay a share of the costs of

drilling and production operations. The share of production to which a working interest owner is entitled will always be smaller than the share of costs that the working interest owner is required to bear, with the balance of the production accruing to the owners of royalties. For example, the owner of a 100% working interest in a lease burdened only by a landowner’s royalty of 12.5% would be required to pay 100% of the costs of a well but would be entitled to retain 87.5% of the production.

      Workover means operations on a producing well to restore or increase production.

PART I

General

      Comstock Resources is a Nevada corporation whose common stock is listed and traded on the New York Stock Exchange and is engaged in the acquisition, development, production and exploration of oil and natural gas.

Available Information

      Our executive offices are located at 5300 Town and Country Blvd., Suite 500, Frisco, Texas 75034. Our telephone number is (972) 668-8800. We file annual, quarterly and current reports, proxy statements and other documents with the SEC under the Securities Exchange Act of 1934. The public may read and copy any materials that we file with the SEC at the SEC’s Public Reference Room at 450 Fifth Street, N.W., Washington, D.C. 20549. The public may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. Also, the SEC maintains an internet website that contains reports, proxy and information statements, and other information regarding issuers, including us, that file electronically with the SEC. The public can obtain any documents that we file with the SEC at http://www.sec.gov. We also make available free of charge on our internet website (http://www.comstockresources.com) our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and, if applicable, amendments to those reports filed or furnished pursuant to Section 13(a) of the Exchange Act as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC.

Summary Reserve and Production Information

      Our oil and natural gas operations are concentrated in the Gulf of Mexico, East Texas/ North Louisiana, Southeast Texas and South Texas regions. In addition, we have properties in the Mid-Continent region located in the Texas panhandle, Oklahoma, Arkansas and Kansas and in other regions. Our oil and natural gas properties are estimated to have proved reserves of 628.8 Bcfe with an estimated PV 10 Value of $1.5 billion as of December 31, 2004 and a standardized measure of discounted future net cash flows of $1.1 billion (see note 1 on page 15 for a discussion of our PV 10 Value and our standardized measure of discounted future net cash flows). Our proved oil and natural gas reserve base is 85% natural gas and 67% proved developed on a Bcfe basis as of December 31, 2004.

      Our proved reserves at December 31, 2004 and our 2004 average daily production are summarized below by our operating regions:

Strengths

      High Quality Properties. Our operations are focused in four geographically concentrated areas, the Gulf of Mexico, East Texas/ North Louisiana, Southeast Texas and South Texas regions, which account for

approximately 29%, 32%, 18% and 8% of our proved reserves, respectively. We have high price realizations relative to benchmark prices for natural gas and crude oil production. We also have favorable operating costs, which result in us having high cash margins. Finally, our properties have an average reserve life of approximately 14.7 years and have extensive development and exploration potential.

      Successful Exploration and Development Program. In 2004, we spent $94.6 million on the exploitation and development of our oil and natural gas properties for development drilling, recompletions, workovers, abandonment and production facilities. Overall, we drilled 46 development wells, 20.9 net to us, with a 98% success rate. We also had a successful exploratory drilling program in 2004, spending a total of $47.0 million on exploration to drill 24 wells, 10.0 net to us, with a 54% success rate.

      Successful Acquisitions. We have had significant growth over the years as a result of acquisitions. Since 1991, we have added 766.9 Bcfe of proved oil and natural gas reserves from 31 acquisitions at an average cost of $0.87 per Mcfe. Our application of strict economic and reserve risk criteria have enabled us to successfully evaluate and integrate acquisitions.

      Efficient Operator. We operate 83% of our proved oil and natural gas reserve base as of December 31, 2004 based on the PV 10 Value of our proved reserves. This allows us to control operating costs, the timing and plans for future development, the level of drilling and lifting costs and the marketing of production. As an operator, we receive reimbursements for overhead from other working interest owners, which reduces our general and administrative expenses.

      High Price Realizations. The majority of our wells are located in areas in which we can access attractive natural gas and crude oil markets. In addition, our natural gas production has a relatively high Btu content of approximately 1.08 Btu. Our crude oil production has a favorable gravity of approximately 40 degrees. Due to these factors, we have relatively high price realizations compared to benchmark prices. In 2004, the average natural gas price we realized was $5.98 per Mcf, which represented a $0.16 discount to the 2004 NYMEX average monthly settlement price. Also in 2004, the average price we realized for our crude oil was $39.86 per barrel, which represented a $1.75 barrel premium to the average monthly West Texas Intermediate crude oil price for 2004 posted by Koch Industries, Inc.

      High Cash Margins. As a result of our quality properties, higher price realizations and efficient operations, we have higher cash margins than many of our competitors. Consequently, our oil and natural gas reserves have a higher value per Mcfe than reserves that generate lower cash margins.

Business Strategy

      Exploit Existing Reserves. We seek to maximize the value of our oil and natural gas properties by increasing production and recoverable reserves through active workover, recompletion and exploitation activities. We use advanced industry technology, including 3-D seismic data, improved logging tools, and formation stimulation techniques. During 2004, we spent approximately $68.6 million to drill 46 development wells, 20.9 net to us, of which 45 wells, 20.6 net to us, were successful, representing a 98% success rate. In addition, we spent approximately $26.0 million for new production facilities, leasehold costs and for recompletion, abandonment and workover activities. For 2005, we have budgeted $92.0 million for development drilling and for recompletion, abandonment and workover activities.

      Pursue Exploration Opportunities. We conduct exploration activities to grow our reserve base and to replace our production each year. In 2004, we spent approximately $47.0 million to drill 24 exploratory wells, 10.0 net to us, of which 13 wells, 5.5 net to us, were successful, representing a 54% success rate. We have budgeted $83.0 million for exploration activities in 2005, which will be focused primarily in our Gulf of Mexico, Southeast Texas and South Texas regions.

      Maintain Low Cost Structure. We seek to increase cash flow by carefully controlling operating costs and general and administrative expenses. Our average oil and gas operating costs per Mcfe were $1.22 in 2004 and our general and administrative expenses per Mcfe (excluding stock based compensation) averaged $0.20 in 2004.

      Acquire High Quality Properties at Attractive Costs. We have a successful track record of increasing our oil and natural gas reserves through opportunistic acquisitions. Since 1991, we have added 766.9 Bcfe of proved oil and natural gas reserves from 31 acquisitions at a total cost of $665.8 million, or $0.87 per Mcfe. The properties were acquired at an average of 63% of their PV 10 Value in the year the acquisitions were completed by us. We apply strict economic and reserve risk criteria in evaluating acquisitions. We target properties in our core operating areas with established production and low operating costs that also have potential opportunities to increase production and reserves through exploration and exploitation activities.

      Maintain Flexible Capital Expenditure Budget. The timing of most of our capital expenditures is discretionary because we have not made any significant long-term capital expenditure commitments. Consequently, we have a significant degree of flexibility to adjust the level of such expenditures according to market conditions. We anticipate spending approximately $175.0 million on development and exploration projects in 2005. We intend to primarily use operating cash flow to fund our drilling expenditures in 2005. We may also make additional property acquisitions that would require additional sources of funding. Such sources may include borrowings under our bank credit facility or sales of our equity or debt securities.

      Reserve Replacement. We replaced 128% of our production of 42.7 Bcfe in 2004 with 54.6 Bcfe of net additions to our proved reserve base from extensions and discoveries (37.5 Bcfe), purchases (41.0 Bcfe), upward revisions to our previous reserve estimates (1.4 Bcfe), and the net decrease due to the formation of Bois d’Arc Energy, LLC to which we contributed certain of our offshore Gulf of Mexico properties (25.3 Bcfe). The proved reserves added in 2004 were 66% developed and 34% undeveloped. Unless we conduct successful exploration and development activities or acquire properties containing proven reserves, our proved reserves will decline as our reserves are depleted. Our historical reserve additions relate to successful wells drilled in our exploration and development program or acquisitions that we make. To the extent our drilling success rate declines or we are unable to complete acquisitions of productive oil and gas properties, we may not be able to replace all of our production in the future. The production of reserves we added in 2004 are expected to occur during the period from 2005 to 2079. The ultimate recovery of the reserves is subject to future declines in prices of oil and natural gas, which could impact the economic viability of the future operation of the properties and our access to future development capital that will be required to recover additional undeveloped reserves. The annual reserve replacement ratio is calculated by dividing our annual proved reserve additions by our annual production. We use the annual reserve replacement ratio in assessing whether our proved reserve base is expanding or declining. This ratio’s measurement of reserve growth is accurate only to the extent that the reserve additions reflected in a particular year are ultimately recovered and not adjusted upward or downward in the future based on changes to oil and natural gas prices or other factors that may impact the ultimate recovery of such reserves.

Primary Operating Areas

      Our activities are concentrated in four primary operating areas: Gulf of Mexico, East Texas/ North Louisiana, Southeast Texas and South Texas. The following table summarizes the estimated proved oil and natural gas reserves for our five largest offshore fields and our 15 largest onshore fields as of December 31, 2004: