<PAGE>   1

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                                 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 JUNE 30, 2001

                                       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 1-2745

                                ---------------

                          SOUTHERN NATURAL GAS COMPANY
             (Exact Name of Registrant as Specified in its Charter)

<Table>
<S>                                                 <C>
                     DELAWARE                                           63-0196650
          (State or Other Jurisdiction of                            (I.R.S. Employer
          Incorporation or Organization)                            Identification No.)
</Table>

<Table>
<S>                                                 <C>
                 EL PASO BUILDING
               1001 LOUISIANA STREET                                       77002
                  HOUSTON, TEXAS                                        (Zip Code)
     (Address of Principal Executive Offices)
</Table>

       Registrant's Telephone Number, Including Area Code: (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 [X]  No [ ]

     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 $3.75 per share. Shares outstanding on August 6,
2001: 1,000

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

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<PAGE>   2

                        PART I -- FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

                          SOUTHERN NATURAL GAS COMPANY

                  CONDENSED CONSOLIDATED STATEMENTS OF INCOME
                                 (IN MILLIONS)
                                  (UNAUDITED)

<Table>
<Caption>
                                                           QUARTER ENDED       SIX MONTHS ENDED
                                                              JUNE 30,             JUNE 30,
                                                           --------------      ----------------
                                                           2001      2000      2001       2000
                                                           ----      ----      -----      -----
<S>                                                        <C>       <C>       <C>        <C>
Operating revenues.......................................  $94       $97       $205       $205
                                                           ---       ---       ----       ----
Operating expenses
  Operation and maintenance..............................   41        41         87         82
  Depreciation, depletion, and amortization..............   11        10         21         13
  Taxes, other than income taxes.........................    4         6         10         11
                                                           ---       ---       ----       ----
                                                            56        57        118        106
                                                           ---       ---       ----       ----
Operating income.........................................   38        40         87         99
                                                           ---       ---       ----       ----
Other income
  Earnings from unconsolidated affiliates................    4         4          7          9
  Other, net.............................................    2         1          5         (2)
                                                           ---       ---       ----       ----
                                                             6         5         12          7
                                                           ---       ---       ----       ----
Income before interest, income taxes, and other
  charges................................................   44        45         99        106
                                                           ---       ---       ----       ----
Non-affiliated interest and debt expense.................   12         9         23         19
Affiliated interest income, net..........................   (6)       (1)       (10)        --
Income taxes.............................................   15        15         33         34
                                                           ---       ---       ----       ----
                                                            21        23         46         53
                                                           ---       ---       ----       ----
Income before extraordinary items........................   23        22         53         53
Extraordinary items, net of income taxes.................   --        --         --         12
                                                           ---       ---       ----       ----
Net income...............................................  $23       $22       $ 53       $ 65
                                                           ===       ===       ====       ====
</Table>

                            See accompanying notes.

                                        1
<PAGE>   3

                          SOUTHERN NATURAL GAS COMPANY

                     CONDENSED CONSOLIDATED BALANCE SHEETS
                      (IN MILLIONS, EXCEPT SHARE AMOUNTS)
                                  (UNAUDITED)

<Table>
<Caption>
                                                              JUNE 30,   DECEMBER 31,
                                                                2001         2000
                                                              --------   ------------
<S>                                                           <C>        <C>
                                       ASSETS

Current assets
  Cash and cash equivalents.................................   $   --       $   --
  Accounts and notes receivable, net
    Customer................................................       46           74
    Affiliates..............................................      453          214
    Other...................................................        3            9
  Materials and supplies....................................       14           15
  Regulatory assets.........................................       28           27
  Other.....................................................        1           --
                                                               ------       ------
         Total current assets...............................      545          339
                                                               ------       ------
Property, plant, and equipment, at cost.....................    2,588        2,529
Less accumulated depreciation, depletion, and
  amortization..............................................    1,334        1,313
                                                               ------       ------
         Total property, plant, and equipment, net..........    1,254        1,216
                                                               ------       ------
Other assets
  Investments in unconsolidated affiliates..................      112          105
  Other.....................................................       34           12
                                                               ------       ------
                                                                  146          117
                                                               ------       ------
         Total assets.......................................   $1,945       $1,672
                                                               ======       ======

                        LIABILITIES AND STOCKHOLDER'S EQUITY

Current liabilities
  Accounts payable
    Trade...................................................   $   34       $   37
    Affiliates..............................................       12           11
    Other...................................................        2            2
  Current maturities of long-term debt......................      200          100
  Taxes payable.............................................      107           91
  Accrued interest..........................................       28           24
  Other.....................................................        4            4
                                                               ------       ------
         Total current liabilities..........................      387          269
                                                               ------       ------
Long-term debt, less current maturities.....................      499          399
                                                               ------       ------
Deferred income taxes.......................................      134          120
                                                               ------       ------
Other.......................................................       55           67
                                                               ------       ------
Commitments and contingencies
Stockholder's equity
  Common stock, par value $3.75 per share; authorized and
    issued 1,000 shares.....................................       --           --
  Additional paid-in capital................................      102          102
  Retained earnings.........................................      768          715
                                                               ------       ------
         Total stockholder's equity.........................      870          817
                                                               ------       ------
         Total liabilities and stockholder's equity.........   $1,945       $1,672
                                                               ======       ======
</Table>

                            See accompanying notes.

                                        2
<PAGE>   4

                          SOUTHERN NATURAL GAS COMPANY

                CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                                 (IN MILLIONS)
                                  (UNAUDITED)

<Table>
<Caption>
                                                              SIX MONTHS ENDED
                                                                  JUNE 30,
                                                              ----------------
                                                              2001       2000
                                                              -----      -----
<S>                                                           <C>        <C>
Cash flows from operating activities
  Net income................................................  $ 53       $ 65
  Adjustments to reconcile net income to net cash from
     operating activities
     Depreciation, depletion, and amortization..............    21         13
     Extraordinary items....................................    --        (21)
     Deferred income tax expense (benefit)..................    14        (12)
     Net gain on the sale of assets.........................    (1)        --
     Undistributed earnings of unconsolidated affiliates....    (7)        (9)
  Working capital changes, net of non-cash transactions.....    28        123
  Other.....................................................   (31)       (23)
                                                              ----       ----
          Net cash provided by operating activities.........    77        136
                                                              ----       ----
Cash flows from investing activities
  Purchases of property, plant, and equipment...............   (43)       (39)
  Proceeds from the sale of investments.....................    --        159
  Net change in other affiliated advances receivable........  (243)      (261)
  Net proceeds from the sale of assets......................     9         74
                                                              ----       ----
          Net cash used in investing activities.............  (277)       (67)
                                                              ----       ----
Cash flows from financing activities
  Payments to retire long-term debt.........................  (100)        --
  Proceeds from the issuance of long-term debt..............   300         --
  Net change in other affiliated advances payable...........    --        (70)
                                                              ----       ----
          Net cash provided by (used in) financing
           activities.......................................   200        (70)
                                                              ----       ----
Decrease in cash and cash equivalents.......................    --         (1)
Cash and cash equivalents
  Beginning of period.......................................    --          1
                                                              ----       ----
  End of period.............................................  $ --       $ --
                                                              ====       ====
</Table>

                            See accompanying notes.

                                        3
<PAGE>   5

                          SOUTHERN NATURAL GAS COMPANY

              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                  (UNAUDITED)

1. BASIS OF PRESENTATION

     Our 2000 Annual Report on Form 10-K includes a summary of our significant
accounting policies and other disclosures. You should read it in conjunction
with this Quarterly Report on Form 10-Q. The financial statements as of June 30,
2001, and for the quarters and six months ended June 30, 2001 and 2000, are
unaudited. The balance sheet as of December 31, 2000, is derived from the
audited balance sheet included in our Annual Report on Form 10-K. These
financial statements have been prepared pursuant to the rules and regulations of
the U.S. Securities and Exchange Commission and do not include all disclosures
required by accounting principles generally accepted in the United States. In
our opinion, we have made all adjustments, all of which are of a normal,
recurring nature, to fairly present our interim period results. Information for
interim periods may not necessarily indicate the results of operations for the
entire year due to the seasonal nature of our businesses. The prior period
information also includes reclassifications which were made to conform to the
current period presentation. These reclassifications have no effect on our
reported net income or stockholder's equity.

2. EXTRAORDINARY ITEMS

     During the first quarter of 2000, we sold Sea Robin Pipeline Company to
comply with a Federal Trade Commission (FTC) order related to our former parent
company's merger with El Paso Corporation. Net proceeds from this sale were $71
million, and we recognized an extraordinary gain of $12 million, net of income
taxes of $9 million. In May 2000, we also disposed of our one-third interest in
Destin Pipeline Company to comply with the same FTC order. Net proceeds from
this sale were $159 million, and no material gain or loss was recognized on the
transaction.

3. DEBT AND OTHER CREDIT FACILITIES

     In February 2001, we issued $300 million aggregate principal amount 7.35%
notes due 2031. Proceeds of approximately $297 million, net of issuance costs,
were used to pay off $100 million of our 8.875% notes due 2001 and for operating
requirements.

4. COMMITMENTS AND CONTINGENCIES

  Legal Proceedings

     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 under
report 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. 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). In May 2001, the court denied the defendants' motions to dismiss.

     We and a number of our affiliates were named defendants in Quinque
Operating Company, et al v. Gas Pipelines and Their Predecessors, et al, filed
in 1999 in the District Court of Stevens County, Kansas. This class action
complaint alleges that the defendants mismeasured natural gas volumes and
heating content of natural gas on non-federal and non-Native American lands. The
Quinque complaint was transferred to the same court handling the Grynberg
complaint and has now been sent back to Kansas State Court for further
proceedings.

     We are also a named defendant in numerous lawsuits and a named party in
numerous governmental proceedings arising in the ordinary course of our
business.

                                        4
<PAGE>   6

     While the outcome of the matters discussed above cannot be predicted with
certainty, we do not expect the ultimate resolution of these matters will have a
material adverse effect on our financial position, operating results, or cash
flows.

  Environmental

     We are subject to extensive 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. As of June 30, 2001, we had a reserve of approximately $13 million for
expected remediation costs. In addition, we expect to make capital expenditures
for environmental matters of approximately $7 million in the aggregate for the
years 2001 through 2006. These expenditures primarily relate to compliance with
clean air regulations.

     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 the recorded
reserves are adequate.

  Rates and Regulatory Matters

     In March 2000, the Federal Energy Regulatory Commission (FERC) issued an
order requested by Southern LNG Inc., our wholly owned subsidiary, which
authorized the recommissioning of Southern LNG's Elba Island liquefied natural
gas receiving terminal near Savannah, Georgia. In August 2000, Southern LNG
filed an application with FERC requesting limited amendment to the certificate
issued in March 2000 that would modify sendout facilities at the Elba Island
terminal. FERC issued a preliminary determination on non-environmental issues in
February 2001. In July 2001, FERC issued a final order on the environmental and
marine safety aspects of the proceeding. The estimated cost of the plant
reactivation and sendout modification, as filed with FERC, is approximately $40
million. The anticipated in-service date is October 2001, at which time Southern
LNG will update its proposed rates to reflect actual costs.

     In May 2000, we filed an application with FERC to expand our pipeline
system by 336 million cubic feet of natural gas per day at an estimated cost of
$141 million, to serve new power generation loads being sited by Southern
Company Services in Alabama. Phase I of the project is expected to be in service
in June 2002, and Phase II is expected to be in service in June 2003. We
received a certificate order from FERC in March 2001. In May 2001, we filed a
petition to amend the order requesting authorization to increase the diameter of
several of the loop pipelines from 30-inches to 36-inches and to reduce the
number of miles of loop pipeline from 70 miles to 62 miles, thus reducing the
overall cost of the project by approximately $1 million. In July 2001, FERC
approved this amendment, and the Alabama Municipal Distributors Group and others
filed an appeal of FERC's orders authorizing this project. The appeal was filed
in the D.C. Circuit Court of Appeals.

     In April 2001, we filed an application with FERC to expand our north main
line pipeline system to supply transportation demand services to a simple cycle
electric power generation plant in Calhoun County, Alabama for the summer
months, and Alagasco, one of our customers, and the City of Sylacauga during the
winter months. The additional capacity to provide these services will be created
through a combination of construction of new looping lines, replacement or
uprating of existing pipe, and installation of added compression. The estimated
cost of the project is approximately $26 million with an anticipated in-service
date of June 2003.

     Also in April 2001, we filed an application with FERC seeking authorization
to construct and operate the Cypress Pipeline system in southeastern Georgia and
northern Florida for an estimated cost of $240 million. This 166-mile pipeline
will be capable of transporting 310 million cubic feet of natural gas per day
from our
                                        5
<PAGE>   7

liquefied natural gas receiving terminal at Elba Island in Savannah, Georgia to
interconnections with our South Georgia Lateral; Florida Gas Transmission
Company's pipeline (a jointly owned pipeline of El Paso and Enron Corporation);
Atlanta Gas Light's pipeline near Brunswick, Georgia; and Jacksonville Electric
Authority's new Brandy Branch generating plant near Jacksonville, Florida.
Construction is scheduled to begin in the third quarter of 2002, and the
pipeline's projected in-service date is June 1, 2003.

5. TRANSACTIONS WITH RELATED PARTIES

     We participate in El Paso's cash management program which matches
short-term cash excesses and requirements of participating affiliates, thus
minimizing total borrowing from outside sources. We had advanced $451 million at
June 30, 2001, at a market rate of interest which was 4.2% at June 30, 2001. At
December 31, 2000, we had advanced $208 million.

     At June 30, 2001, we had accounts receivable from other related parties of
$2 million and $6 million at December 31, 2000. In addition, we had accounts
payable to other related parties of $12 million at June 30, 2001, versus $11
million at December 31, 2000. These balances were incurred in the normal course
of business.

6. NEW ACCOUNTING PRONOUNCEMENTS NOT YET ADOPTED

  Business Combinations

     In July 2001, the Financial Accounting Standards Board (FASB) issued
Statement of Financial Accounting Standards (SFAS) No. 141, Business
Combinations. This statement requires that all transactions that fit the
definition of a business combination be accounted for using the purchase method
and prohibits the use of the pooling of interests method for all business
combinations initiated after June 30, 2001. This statement also establishes
specific criteria for the recognition of intangible assets separately from
goodwill and requires unallocated negative goodwill to be written off
immediately as an extraordinary item. This standard will have an impact on any
business combination we undertake in the future. We are currently evaluating the
effects of this pronouncement on our historical financial statements.

  Goodwill and Other Intangible Assets

     In July 2001, the FASB issued SFAS No. 142, Goodwill and Other Intangible
Assets. This statement requires that goodwill no longer be amortized but
intermittently tested for impairment at least on an annual basis. Other
intangible assets are to be amortized over their useful life and reviewed for
impairment in accordance with the provisions of SFAS No. 121, Accounting for the
Impairment of Long-Lived Assets and Long-Lived Assets to be Disposed of. An
intangible asset with an indefinite useful life can no longer be amortized until
its useful life becomes determinable. This statement has various effective
dates, the most significant of which is January 1, 2002. We are currently
evaluating the effects of this pronouncement.

  Accounting for Asset Retirement Obligations

     In July 2001, the FASB approved for issuance SFAS No. 143, Accounting for
Asset Retirement Obligations. This statement requires companies to record a
liability relating to the retirement and removal of assets used in their
business. The liability is discounted to the present value, and the related
asset value is increased by the amount of the resulting liability. Over the life
of the asset, the liability will be accreted to its future value and eventually
extinguished when the asset is taken out of service. The provisions of this
statement are effective for fiscal years beginning after June 15, 2002. We are
currently evaluating the effects of this pronouncement.

                                        6
<PAGE>   8

ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
        OF OPERATIONS

     The information contained in Item 2 updates, and you should read it in
conjunction with, information disclosed in Part II, Items 7, 7A, and 8, in our
Annual Report on Form 10-K for the year ended December 31, 2000, in addition to
the financial statements and notes presented in Item 1, Financial Statements, of
this Quarterly Report on Form 10-Q.

                             RESULTS OF OPERATIONS

     During the first quarter of 2000, we completed our sale of Sea Robin
Pipeline Company to comply with an FTC order related to our former parent
company's merger with El Paso. Net proceeds from this sale were $71 million, and
we recognized an extraordinary gain of $12 million, net of income taxes of $9
million. In May 2000, we also disposed of our one-third interest in Destin
Pipeline Company to comply with the same FTC order. Net proceeds from this sale
were $159 million, and no material gain or loss was recognized on the
transaction.

     Below are the operating results and an analysis of those results for the
quarters and six months ended June 30:

<Table>
<Caption>
                                                   QUARTER ENDED      SIX MONTHS ENDED
                                                  ----------------    ----------------
                                                   2001      2000      2001      2000
                                                  ------    ------    ------    ------
                                                  (IN MILLIONS, EXCEPT VOLUME AMOUNTS)
<S>                                               <C>       <C>       <C>       <C>
Operating revenues..............................  $   94    $   97    $  205    $  205
Operating expenses..............................     (56)      (57)     (118)     (106)
Other income, net...............................       6         5        12         7
                                                  ------    ------    ------    ------
  Earnings before interest expense and income
     taxes......................................  $   44    $   45    $   99    $  106
                                                  ======    ======    ======    ======
Throughput volumes (BBtu/d)(1)..................   1,657     2,037     1,943     2,227
                                                  ======    ======    ======    ======
</Table>

---------------
(1) BBtu/d means billion British thermal units per day. Throughput volumes
    exclude our Sea Robin pipeline system sold in March 2000 and our one-third
    interest in the Destin system sold in May 2000 in connection with the merger
    with El Paso.

     In March 2000, FERC issued an order allowing us to reactivate our Elba
Island liquefied natural gas facility. Following the reactivation, we made
adjustments that were previously approved under a FERC order, including
re-establishing costs related to the facility which we were previously ordered
to write off, and eliminating a regulatory asset for future recoveries of our
Elba Island facility costs. As of January 1, 2000, we also stopped recovering
amounts under a minimum bill provision under a prior settlement order.

  Second Quarter 2001 Compared to Second Quarter 2000

     Operating revenues for the quarter ended June 30, 2001, were $3 million
lower than the same period in 2000. The decrease was a result of the elimination
of the minimum bill provisions at Elba Island as a result of its approved
reactivation combined with lower throughput, higher 2000 sales of excess natural
gas, and lower revenue reserve estimates in 2000. Partially offsetting the
decrease was the impact of higher natural gas prices on sales under natural gas
sales contracts.

     Operating expenses for the quarter ended June 30, 2001, were slightly lower
from the same period in 2000. The impact of higher prices on purchases of
natural gas were partially offset by lower corporate allocations following El
Paso's merger with The Coastal Corporation in January 2001.

                                        7
<PAGE>   9

  Six Months Ended 2001 Compared to Six Months Ended 2000

     Operating revenues for the six months ended June 30, 2001, were the same as
those for the same period in 2000. During 2001, revenues increased due to higher
prices on sales of natural gas under natural gas sales contracts. These
increases were offset by lower transportation revenues from the sale of our Sea
Robin system in the first quarter of 2000, lower throughput, lower rates
following our rate case settlement in June of 2000, the elimination of the
minimum bill provisions on our Elba Island facility, higher 2000 sales of excess
natural gas, and lower revenue reserve estimates in 2000.

     Operating expenses for the six months ended June 30, 2001, were $12 million
higher than the same period in 2000. The increase was due to the favorable
impact on depreciation expense of the approval to reactivate our Elba Island
facility and the impact of higher prices on purchases of natural gas. The
increase was partially offset by lower corporate allocations following El Paso's
merger with Coastal, lower depreciation expense following our 2000 rate case
settlement, lower ad valorem and franchise taxes in 2001, and lower operating
expenses from the sale of Sea Robin.

     Other income for the six months ended June 30, 2001, was $5 million higher
than the same period in 2000. The increase was due to the elimination of an
asset for the future recovery of costs established for the Elba Island facility
in the first quarter of 2000 and contract termination fees in the first quarter
of 2001, partially offset by lower equity earnings resulting from the sale of
our one-third interest in Destin Pipeline Company in the second quarter of 2000.

NON-AFFILIATED INTEREST AND DEBT EXPENSE

     Non-affiliated interest and debt expense for the quarter and six months
ended June 30, 2001, was $3 million and $4 million higher than the same periods
in 2000 due to increased long-term borrowings during 2001. See Item 1, Financial
Statements, Note 3 for a further discussion of our borrowing activities.

AFFILIATED INTEREST INCOME, NET

     Affiliated interest income, net for the quarter and six months ended June
30, 2001, was $5 million and $10 million higher than the same periods in 2000
due to increased average advances under our cash management program with El Paso
in 2001 offset by lower short-term interest rates.

INCOME TAXES

     The income tax expenses for the quarters ended June 30, 2001 and 2000, were
$15 million for both periods, resulting in effective tax rates of 39 percent and
40 percent. The income tax expenses for the six months ended June 30, 2001 and
2000, were $33 million and $34 million, resulting in effective tax rates of 38
percent and 39 percent . Our effective tax rates were different than the
statutory rate of 35 percent in all periods due to state income taxes.

                 NEW ACCOUNTING PRONOUNCEMENTS NOT YET ADOPTED

     See Item 1, Financial Statements, Note 6, which is incorporated herein by
reference.

                                        8
<PAGE>   10

CAUTIONARY STATEMENT FOR PURPOSES OF THE "SAFE HARBOR" PROVISIONS OF THE PRIVATE
                    SECURITIES LITIGATION REFORM ACT OF 1995

     This report contains or incorporates by reference forward-looking
statements within the meaning of the Private Securities Litigation Reform Act of
1995. Where any forward-looking statement includes a statement of the
assumptions or bases underlying the forward-looking statement, we caution that,
while we believe these assumptions or bases to be reasonable and to be made in
good faith, assumed facts or bases almost always vary from the actual results,
and the differences between assumed facts or bases and actual results can be
material, depending upon the circumstances. Where, in any forward-looking
statement, we or our management express an expectation or belief as to future
results, that expectation or belief is expressed in good faith and is believed
to have a reasonable basis. We cannot assure you, however, that the statement of
expectation or belief will result or be achieved or accomplished. The words
"believe," "expect," "estimate," "anticipate" and similar expressions will
generally identify forward-looking statements.

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

     This information updates, and you should read it in conjunction with,
information disclosed in Part II, Item 7A in our Annual Report on Form 10-K for
the year ended December 31, 2000, in addition to the information presented in
Items 1 and 2 of this Quarterly Report on Form 10-Q.

     There are no material changes in our quantitative and qualitative
disclosures about market risks from those reported in our Annual Report on Form
10-K for the year ended December 31, 2000.

                                        9
<PAGE>   11

                          PART II -- OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS

     See Part I, Item 1, Financial Information, Note 4, which is incorporated
herein by reference.

ITEM 2. CHANGES IN SECURITIES AND USE OF PROCEEDS

     None.

ITEM 3. DEFAULTS UPON SENIOR SECURITIES

     None.

ITEM 4. SUBMISSION OF MATTERS TO A VOTE OF SECURITY-HOLDERS

     None.

ITEM 5. OTHER INFORMATION

     None.

ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K

a. Exhibits

     None.

     Undertaking

          We hereby undertake, pursuant to Regulation S-K, Item 601(b),
     paragraph (4)(iii), to furnish to the U.S. Securities and Exchange
     Commission, upon request, all constituent instruments defining the rights
     of holders of our long-term debt not filed herewith for the reason that the
     total amount of securities authorized under any of such instruments does
     not exceed 10 percent of our total consolidated assets.

b. Reports on Form 8-K

     None.

                                        10
<PAGE>   12

                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

                                            SOUTHERN NATURAL GAS COMPANY

Date: August 10, 2001                              /s/ GREG G. GRUBER
                                                       Greg G. Gruber
                                                   Senior Vice President
                                                and Chief Financial Officer

Date: August 10, 2001                             /s/ JEFFREY I. BEASON
                                                     Jeffrey I. Beason
                                            Senior Vice President and Controller
                                                 (Chief Accounting Officer)

                                        11