UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-Q

(Mark One)

[X]

 QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended March 31, 2005

OR

[ ]

 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                  to                  

Commission File Number 1-4101

Tennessee Gas Pipeline Company

(Exact Name of Registrant as Specified in its Charter)

Telephone Number: (713) 420-2600

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

      Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date.

      Common stock, par value $5 per share. Shares outstanding on May 11, 2005: 208

      TENNESSEE GAS PIPELINE COMPANY MEETS THE CONDITIONS OF GENERAL INSTRUCTION H(1)(a) AND (b) TO FORM 10-Q AND IS THEREFORE FILING THIS REPORT WITH A REDUCED DISCLOSURE FORMAT AS PERMITTED BY SUCH INSTRUCTION.

TENNESSEE GAS PIPELINE COMPANY

TABLE OF CONTENTS

      Below is a list of terms that are common to our industry and used throughout this document:

     When we refer to cubic feet measurements, all measurements are at a pressure of 14.73 pounds per square inch.

     When we refer to “us”, “we”, “our”, or “ours”, we are describing Tennessee Gas Pipeline Company and/or our subsidiaries.

PART I — FINANCIAL INFORMATION

Item 1. Financial Statements

TENNESSEE GAS PIPELINE COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF INCOME

(In millions)

(Unaudited)

See accompanying notes.

TENNESSEE GAS PIPELINE COMPANY

CONDENSED CONSOLIDATED BALANCE SHEETS

(In millions, except share amounts)

(Unaudited)

See accompanying notes.

TENNESSEE GAS PIPELINE COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(In millions)

(Unaudited)

See accompanying notes.

TENNESSEE GAS PIPELINE COMPANY

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

1. Basis of Presentation and Significant Accounting Policies

  Basis of Presentation

      We are an indirect wholly owned subsidiary of El Paso Corporation (El Paso). We prepared this Quarterly Report on Form 10-Q under the rules and regulations of the United States Securities and Exchange Commission (SEC). Because this is an interim period filing presented using a condensed format, it does not include all of the disclosures required by generally accepted accounting principles. You should read it along with our 2004 Annual Report on Form 10-K, which includes a summary of our significant accounting policies and other disclosures. The financial statements as of March 31, 2005, and for the quarters ended March 31, 2005 and 2004, are unaudited. We derived the balance sheet as of December 31, 2004, from the audited balance sheet filed in our 2004 Annual Report on Form 10-K. In our opinion, we have made all adjustments which are of a normal, recurring nature to fairly present our interim period results. Due to the seasonal nature of our business, information for interim periods may not be indicative of our results of operations for the entire year.

  Significant Accounting Policies

      Our significant accounting policies are consistent with those discussed in our 2004 Annual Report on Form 10-K.

  New Accounting Pronouncements Issued But Not Yet Adopted

      As of March 31, 2005, there were several accounting standards and interpretations that had not yet been adopted by us. Below is a discussion of a significant standard that may impact us.

      Accounting for Asset Retirement Obligations. In March 2005, the Financial Accounting Standards Board (FASB) issued FASB Interpretation (FIN) No. 47, Accounting for Conditional Asset Retirement Obligations. FIN No. 47 requires companies to record a liability for those asset retirement obligations in which the timing or amount of settlement of the obligation are uncertain. These conditional obligations were not addressed by Statement of Financial Accounting Standards No. 143, which we adopted on January 1, 2003. FIN No. 47 will require us to accrue a liability when a range of scenarios indicate that the potential timing and settlement amounts of our conditional asset retirement obligations can be determined. We will adopt the provisions of this standard in the fourth quarter of 2005 and have not yet determined the impact, if any, that this pronouncement will have on our financial statements.

2. Credit Facilities

      We are an eligible borrower under El Paso’s $3 billion credit agreement. At March 31, 2005, El Paso had $1.2 billion outstanding under the term loan and $1.4 billion of letters of credit issued under the credit agreement, none of which was borrowed by or issued on behalf of us. For a further discussion of El Paso’s $3 billion credit agreement and our restrictive covenants, see our 2004 Annual Report on Form 10-K.

3. Commitments and Contingencies

  Legal Proceedings

      Grynberg. In 1997, we and a number of our affiliates were named defendants in actions brought by Jack Grynberg on behalf of the U.S. Government under the False Claims Act. Generally, these complaints allege an industry-wide conspiracy to underreport the heating value as well as the volumes of the natural gas produced from federal and Native American lands, which deprived the U.S. Government of royalties. The plaintiff in this case seeks royalties that he contends the government should have received had the volume and heating value been differently measured, analyzed, calculated and reported, together with interest, treble

damages, civil penalties, expenses and future injunctive relief to require the defendants to adopt allegedly appropriate gas measurement practices. No monetary relief has been specified in this case. These matters have been consolidated for pretrial purposes (In re: Natural Gas Royalties Qui Tam Litigation, U.S. District Court for the District of Wyoming, filed June 1997). Motions to dismiss have been briefed and argued and the parties are awaiting the court’s ruling. Our costs and legal exposure related to these lawsuits and claims are not currently determinable.

      Will Price (formerly Quinque). We and a number of our affiliates are named defendants in Will Price, et al. v. Gas Pipelines and Their Predecessors, et al., filed in 1999 in the District Court of Stevens County, Kansas. Plaintiffs allege that the defendants mismeasured natural gas volumes and heating content of natural gas on non-federal and non-Native American lands and seek to recover royalties that they contend they should have received had the volume and heating value of natural gas produced from their properties been differently measured, analyzed, calculated and reported, together with prejudgment and postjudgment interest, punitive damages, treble damages, attorneys’ fees, costs and expenses, and future injunctive relief to require the defendants to adopt allegedly appropriate gas measurement practices. No monetary relief has been specified in this case. Plaintiffs’ motion for class certification of a nationwide class of natural gas working interest owners and natural gas royalty owners was denied in April 2003. Plaintiffs were granted leave to file a Fourth Amended Petition, which narrows the proposed class to royalty owners in wells in Kansas, Wyoming and Colorado and removes claims as to heating content. A second class action petition has since been filed as to the heating content claim. Motions for class certification have been briefed and argued in both proceedings, and the parties are awaiting the court’s ruling. Our costs and legal exposure related to these lawsuits and claims are not currently determinable.

      In addition to the above matters, we and our subsidiaries and affiliates are named defendants in numerous lawsuits and governmental proceedings that arise in the ordinary course of our business.

      For each of our outstanding legal matters, we evaluate the merits of the case, our exposure to the matter, possible legal or settlement strategies and the likelihood of an unfavorable outcome. If we determine that an unfavorable outcome is probable and can be estimated, we establish the necessary accruals. As further information becomes available, or other relevant developments occur, we adjust our accrual amounts accordingly. While there are still uncertainties related to the ultimate costs we may incur, based upon our evaluation and experience to date, we had no accruals for our outstanding legal matters at March 31, 2005.

  Environmental Matters

      We are subject to federal, state and local laws and regulations governing environmental quality and pollution control. These laws and regulations require us to remove or remedy the effect on the environment of the disposal or release of specified substances at current and former operating sites. At March 31, 2005, we had accrued approximately $41 million, including approximately $40 million for expected remediation costs and associated onsite, offsite and groundwater technical studies, and approximately $1 million for related environmental legal costs, which we anticipate incurring through 2027. Our accrual was based on the most likely outcome that can be reasonably estimated. Below is a reconciliation of our accrued liability from January 1, 2005 to March 31, 2005 (in millions):

      For the remainder of 2005, we estimate that our total remediation expenditures will be approximately $6 million, which will be expended under government directed clean-up plans. In addition, we expect to make capital expenditures for environmental matters of approximately $33 million in the aggregate for the years 2005 through 2009. These expenditures primarily relate to compliance with clean air regulations.

      Polychlorinated Biphenyls (PCB) Cost Recoveries. Pursuant to a consent order executed by us in 1994 with the Environmental Protection Agency (EPA), we have been conducting various remediation activities

associated with the presence of PCB and certain hazardous materials at certain of our compressor stations. In May 1995, following negotiations with our customers, we filed an agreement with the Federal Energy Regulatory Commission (FERC) that established a mechanism for recovering a substantial portion of the environmental costs identified in our PCB remediation project. The agreement, which was approved by the FERC in November 1995, provided for a PCB surcharge on firm and interruptible customers’ rates to pay for eligible remediation costs, with these surcharges to be collected over a defined collection period. We have received approval from the FERC to extend the collection period, which is now currently set to expire in June 2006. The agreement also provided for bi-annual audits of eligible costs. As of March 31, 2005, we had pre-collected PCB costs by approximately $127 million. This pre-collected amount will be reduced by future eligible costs incurred for the remainder of the remediation project. To the extent actual eligible expenditures are less than the amounts pre-collected, we will refund to our customers the difference, plus carrying charges incurred up to the date of the refunds. At March 31, 2005, we have recorded a regulatory liability (included in other non-current liabilities on our balance sheet) of $99 million for our estimated future refund obligations.

      Kentucky PCB Project. In November 1988, the Kentucky Natural Resources and Environmental Protection Cabinet filed a complaint in a Kentucky state court alleging that we discharged pollutants into the waters of the state and disposed of PCBs without a permit. The agency sought an injunction against future discharges, an order to remediate or remove PCBs and a civil penalty. We entered into interim agreed orders with the agency to resolve many of the issues raised in the complaint. The relevant Kentucky compressor stations are being remediated under a 1994 consent order with the EPA. Despite our remediation efforts, the agency may raise additional technical issues or seek additional remediation work and/or penalties in the future.

      CERCLA Matters. We have received notice that we could be designated, or have been asked for information to determine whether we could be designated, as a Potentially Responsible Party (PRP) with respect to three active sites under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) or state equivalents. We have sought to resolve our liability as a PRP at these sites through indemnification by third parties and settlements which provide for payment of our allocable share of remediation costs. As of March 31, 2005, we have estimated our share of the remediation costs at these sites to be approximately $1 million. Since the clean-up costs are estimates and are subject to revision as more information becomes available about the extent of remediation required, and because in some cases we have asserted a defense to any liability, our estimates could change. Moreover, liability under the federal CERCLA statute is joint and several, meaning that we could be required to pay in excess of our pro rata share of remediation costs. Our understanding of the financial strength of other PRPs has been considered, where appropriate, in estimating our liabilities. Accruals for these matters are included in the environmental reserve discussed above.

      It is possible that new information or future developments could require us to reassess our potential exposure related to environmental matters. We may incur significant costs and liabilities in order to comply with existing environmental laws and regulations. It is also possible that other developments, such as increasingly strict environmental laws and regulations and claims for damages to property, employees, other persons and the environment resulting from our current or past operations, could result in substantial costs and liabilities in the future. As this information becomes available, or other relevant developments occur, we will adjust our accrual amounts accordingly. While there are still uncertainties relating to the ultimate costs we may incur, based upon our evaluation and experience to date, we believe our reserves are adequate.

  Rates and Regulatory Matters

      Accounting for Pipeline Integrity Costs. In November 2004, the FERC issued a proposed accounting release that may impact certain costs we incur related to our pipeline integrity program. If the release is enacted as written, we would be required to expense certain future pipeline integrity costs instead of capitalizing them as part of our property, plant and equipment. Although we continue to evaluate the impact that this potential accounting release will have on our consolidated financial statements, we currently estimate that we would be required to expense an additional amount of pipeline integrity expenditures in the range of approximately $7 million to $15 million annually over the next eight years.

      Selective Discounting Notice of Inquiry. In November 2004, the FERC issued a Notice of Inquiry (NOI) seeking comments on its policy regarding selective discounting by natural gas pipelines. The FERC seeks comments regarding whether its practice of permitting pipelines to adjust their ratemaking throughput downward in rate cases to reflect discounts given by pipelines for competitive reasons is appropriate when the discount is given to meet competition from another natural gas pipeline. We, along with several of our affiliated pipelines, filed comments on the NOI in March 2005. The final outcome of this inquiry cannot be predicted with certainty, nor can we be predict the impact that the final rule will have on us.

      While the outcome of our outstanding rates and regulatory matters cannot be predicted with certainty, based on current information, we do not expect the ultimate resolution of these matters to have a material adverse effect on our financial position, operating results or cash flows. However, it is possible that new information or future developments could require us to reassess our potential exposure related to these matters, which could have a material effect on our results of operations, our financial position, and our cash flows in the periods these events occur.

Guarantees

      We are involved in various joint ventures and other ownership arrangements that sometimes require additional financial support that results in the issuance of financial and performance guarantees. See our 2004 Annual Report on Form 10-K for a description of these guarantees. As of March 31, 2005, we had approximately $8 million of both financial and performance guarantees not otherwise reflected in our financial statements.

4. Investment in Unconsolidated Affiliate and Transactions with Affiliates

      We have a 50 percent ownership interest in Bear Creek Storage Company. We account for this investment using the equity method of accounting. Summarized income statement information of our proportionate share of the income of this investment for the quarters ended March 31 is as follows:

  Transactions with Affiliates

      Cash Management Program. We participate in El Paso’s cash management program which matches short-term cash surpluses and needs of participating affiliates, thus minimizing total borrowings from outside sources. At March 31, 2005 and December 31, 2004, we had advanced $965 million and $928 million to El Paso. The interest rate at March 31, 2005 and December 31, 2004 was 3.5% and 2.0%. This receivable is due upon demand; however, at March 31, 2005 and December 31, 2004, we have classified this advance as a non-current note receivable from affiliates because we do not anticipate settlement within the next twelve months.

      Taxes. We are a party to a tax accrual policy with El Paso whereby El Paso files U.S. and certain state tax returns on our behalf. In certain states, we file and pay directly to the state taxing authorities. We have state income taxes receivable of $3 million at March 31, 2005 and $28 million at December 31, 2004, which are included in accounts and notes receivable — other on our balance sheets. We have federal income taxes payable of $55 million at March 31, 2005 and $46 million at December 31, 2004, which are included in taxes payable on our balance sheets. The majority of these balances will become payable to or receivable from El Paso.

      Other Affiliate Balances. The following table shows other balances with our affiliates:

      Affiliate Revenues and Expenses. The following table shows revenues and charges from our affiliates for the quarters ended March 31:

      The information contained in Item 2 updates, and should be read in conjunction with, the information disclosed in our 2004 Annual Report on Form 10-K, and the financial statements and notes presented in Item 1 of this Quarterly Report on Form 10-Q.

Results of Operations

      Our management, as well as El Paso’s management, uses earnings before interest expense and income taxes (EBIT) to assess the operating results and effectiveness of our business. We define EBIT as net income adjusted for (i) items that do not impact our income from continuing operations, (ii) income taxes, (iii) interest and debt expense and (iv) affiliated interest income. Our business consists of consolidated operations as well as an investment in an unconsolidated affiliate. We exclude interest and debt expense from this measure so that our management can evaluate our operating results without regard to our financing methods. We believe the discussion of our results of operations based on EBIT is useful to our investors because it allows them to more effectively evaluate the operating performance of both our consolidated business and our unconsolidated investment using the same performance measure analyzed internally by our management. EBIT may not be comparable to measurements used by other companies. Additionally, EBIT should be considered in conjunction with net income and other performance measures such as operating income or operating cash flows.

      The following is a reconciliation of EBIT to net income for the quarters ended March 31:

      The following items contributed to our overall EBIT decrease of $30 million for the quarter ended March 31, 2005 as compared to the same period in 2004: