<PAGE>

                  U.S. Securities and Exchange Commission
                             Washington, D.C. 20549

                                   Form 10-QSB

                                   (Mark One)

        [ X ]  QUARTERLY REPORT PURSUANT SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

                 For the quarterly period ended June 30, 2000



        [   ]  TRANSITION REPORT PURSUANT SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934
               For the transition period from _________ to _________

                        Commission file number 333-31681

                 Atlas-Energy for the Nineties-Public #6 Ltd.
                (Name of small business issuer in its charter)

            Pennsylvania                             23-2888337
     (State or other jurisdiction of      (I.R.S. Employer identification No.)
      incorporated or organization)

               311 Rouser Road, Moon Township, Pennsylvania 15108
               (Address of principal executive offices)   (Zip Code)

                        Issuer's telephone (412) 262-2830

(Former name, former address and former fiscal year, if changed since last
report)

Check whether the issuer (1) filed all reports required to be filed by Section
13 or 15(d) of the Exchange Act during the past 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

Transitional Small Business Disclosure Format (check one):

Yes  X   No

===============================================================================

<PAGE>

                                     PART I

Item 1.  Financial Statements

The unaudited Financial Statements of Atlas-Energy for the Nineties-Public #6
Ltd. (the "Partnership") for the period January 1, 2000 to June 30, 2000.

Item 2.  Description of Business

The Partnership has placed into production 44.45 net wells to the
Clinton/Medina formation in Mercer and Lawrence Counties, Pennsylvania. As of
June 30, 2000, all 44.45 net wells are in production. The first quarterly
distribution was on June 8, 1998 for natural gas production during January,
February and March, 1998.

Natural gas sales revenue for the three months was $336,857 which includes
landowner royalties. Expenses for this period include $75.00 per month per
well for administrative costs and $275.00 per month per well for pumpers
fees.

For the next twelve months management believes that the Partnership has
adequate capital. No other wells will be drilled and, therefore, no
additional funds will be required.

Although management does not anticipate that the Partnership will have to do
so, any additional funds which may be required will be obtained from
production revenues from Partnership wells or from borrowings by the
Partnership from Atlas or its affiliates, although Atlas is not contractually
committed to make such a loan. No borrowings will be obtained from third
parties.

                                     PART II

Item 1.  Legal Proceeding
         None

Item 2.  Changes in Securities
         None

Item 3.  Defaults Upon Senior Securities
         None

Item 4.  Submission of Matters to a Vote of Securities Holders
         None

Item 5.  Other Matters
         None

Item 6.  Reports on Form 8-K
         The registrant filed no reports on Form 8-K during the last quarter
         of the period covered by this report.

<PAGE>

10-Aug-00

                  ATLAS-ENERGY FOR THE NINETIES--PUBLIC #6 LTD.
                       A PENNSYLVANIA LIMITED PARTNERSHIP
                                  BALANCE SHEET
                    AS OF JUNE 30, 2000 and DECEMBER 31, 1999

<TABLE>
<CAPTION>
                                                                                    JUNE 30
                                                                                     2000           December 31        Increase
                                                                                  (unaudited)          1999           (Decrease)
                                                                             -------------------------------------------------------
<S>                                                                          <C>                  <C>              <C>
ASSETS

CURRENT ASSETS

     Cash                                                                     $          18,640     $     14,662    $       3,978
     Accounts receivable                                                                291,868          298,026           (6,158)

                                                                             --------------------  -------------    --------------
                    TOTAL CURRENT ASSETS                                                310,508          312,688           (2,180)

     Oil and gas drilling contracts/leases,net of accum. depl. & amort.               7,596,362        7,982,685         (386,323)


                                                                             --------------------  -------------    --------------
                    TOTAL ASSETS                                              $       7,906,870     $  8,295,373     $   (388,503)
                                                                             =====================================================


LIABILITIES AND PARTNERS' CAPITAL


     Accounts payable                                                         $          30,730     $     14,775     $     15,955
     Partners' capital                                                                7,876,140        8,280,598         (404,458)
                                                                             --------------------  -------------    --------------
                    TOTAL LIABILITIES AND PARTNERS' CAPITAL                   $       7,906,870     $  8,295,373     $   (388,503)
                                                                             =====================================================
</TABLE>


The notes to Financial Statements are an integral part of this statement.

<PAGE>

                ATLAS-ENERGY FOR THE NINETIES--PUBLIC #6 LTD.
                      A PENNSYLVANIA LIMITED PARTNERSHIP
                                   STATEMENT OF INCOME (Unaudited)
                FOR THE SIX MONTHS ENDED JUNE  30, 2000 AND 1999

<TABLE>
<CAPTION>

                                                                 Six Months Ended                Second Quarter Ended
                                                                      June 30        June 30            June 30           June 30
REVENUE                                                                 2000           1999              2000              1999
                                                                 -------------------------------   --------------------------------
<S>                                                              <C>                <C>          <C>                   <C>
      Natural gas sales                                               $668,269       $754,372          $336,857         $354,973
      Interest income                                                    7,100          5,312             4,796            2,145
                                                                 -------------    -----------      -------------    ---------------
                Total Revenue                                          675,369        759,684           341,653          357,118

EXPENSES

     Well operating expense                                             97,176         96,320            44,989           46,743
     Depletion and depreciation of oil and gas wells and leases        386,323        581,206           188,845          266,746
     General and administrative fees                                    19,815         19,290             9,889           10,189
     Professional fees                                                  16,398          7,895            16,398            3,645

     Other                                                                 543            798               362              501
                                                                 -------------    -----------      -------------    ---------------
                Total Expenses                                         520,255        705,509           260,483          327,824
                                                                 -------------    -----------      -------------    ---------------
Net Earnings                                                         $ 155,114       $ 54,175          $ 81,170         $ 29,294
                                                                 =============    ===========      =============    ===============
</TABLE>

The notes to Financial Statements are an integral part of this statement.

<PAGE>

                  ATLAS-ENERGY FOR THE NINETIES--PUBLIC #6 LTD.
                       A PENNSYLVANIA LIMITED PARTNERSHIP
                       STATEMENT OF CASH FLOWS (Unaudited)
                 FOR THE SIX MONTHS ENDED JUNE 30, 2000 AND 1999

<TABLE>
<CAPTION>
                                                                                         Six Months Ended
                                                                                             June 30
                               Increase (Decrease) in Cash
                                                                                     2000                1999
                                                                             -----------------------------------------
<S>                                                                          <C>                      <C>
Cash flows from operating activities
     Net Earnings                                                                 $ 155,114             $54,175
     Adjustments to reconcile net earnings to net cash
       provided by operating activities:

                Depletion and depreciation                                          386,323             581,206

                Decrease  in accounts receivable                                      6,158             135,995
                Increase  in accounts payable                                        15,955                 706
                                                                                 ----------          ----------
Cash provided by operating activities                                               563,550             772,082

Cash flows used in financing activities:
     Distributions to Partners                                                     (559,572)           (768,744)
                                                                                 ----------          ----------

Net Increase  in Cash                                                                 3,978               3,338

Cash at beginning of period                                                          14,662               7,960
                                                                                 ----------          ----------

Cash at end of period                                                               $18,640             $11,298
                                                                                 ==========          ==========
</TABLE>

The notes to Financial Statements are an integral part of this statement.

<PAGE>

                 ATLAS-ENERGY FOR THE NINETIES--PUBLIC #6 LTD.
                       A PENNSYLVANIA LIMITED PARTNERSHIP
       STATEMENT OF CHANGES IN PARTNERS' CAPITAL ACCOUNTS (Unaudited)
                         FOR THE SIX MONTHS ENDED JUNE 30, 2000

<TABLE>
<CAPTION>
                                                                                   MANAGING
                                                                                    GENERAL            OTHER
                                                                                   PARTNER            PARTNERS            TOTAL
                                                                                  ----------         ----------        ----------
<S>                                                                               <C>                <C>              <C>
BALANCE AT JANUARY 1, 2000                                                          $331,143         $7,949,455        $8,280,598


Participation in revenue and expenses:

                 Net Production Revenues                                             142,773            428,319           571,092
                 Interest                                                              1,775              5,325             7,100
                 Depletion and depreciation                                          (73,423)          (312,899)         (386,322)
                 Other costs                                                          (9,189)           (27,567)          (36,756)
                                                                                  ----------         ----------        ----------
Net Earnings                                                                          61,936             93,178           155,114

Distributions                                                                       (139,893)          (419,679)         (559,572)
                                                                                  ----------         ----------        ----------
BALANCE AT JUNE 30, 2000                                                            $253,186         $7,622,954        $7,876,140
                                                                                  ==========         ==========        ==========
</TABLE>

The notes to Financial Statements are an integral part of this statement.

<PAGE>

                    NOTES TO FINANCIAL STATEMENTS (UNAUDITED)

                  ATLAS-ENERGY FOR THE NINETIES--PUBLIC #6 LTD.
                       A PENNSYLVANIA LIMITED PARTNERSHIP

1.       INTERIM FINANCIAL STATEMENTS

         The financial statements as of June 30, 2000 and for the six months
then ended have been prepared by the management of the Partnership without
audit, pursuant to the rules and regulations of the Securities and Exchange
Commission. Certain information and footnote disclosures normally included in
the financial statements prepared in accordance with generally accepted
accounting principles have been omitted pursuant to such rules and
regulations, although the partnership believes that the disclosures are
adequate to make the information presented not misleading. These financial
statements should be read in conjunction with the audited December 31, 1999
financial statements. In the opinion of management, all adjustments
(consisting of only normal recurring accruals) considered necessary for
presentation have been included.

2.       SIGNIFICANT ACCOUNTING POLICIES

         The Partnership uses the successful efforts method of accounting for
oil and gas activities. Costs to acquire mineral interests in oil and gas
properties and drill and equip wells are capitalized. Oil and gas properties
are periodically assessed and when unamortized costs exceed expected future
net cash flows, a loss is recognized by a charge to income.

         Capitalized costs of oil and gas wells and leases are depreciated,
depleted and amortized by the unit of production method.

<PAGE>

                      MANAGEMENT'S DISCUSSION AND ANALYSIS
                OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS
                  ATLAS-ENERGY FOR THE NINETIES-PUBLIC #6 LTD.

Management's discussion and analysis should be read in conjunction with the
financial statements and notes thereto.

RESULTS OF OPERATIONS

SIX MONTHS ENDED JUNE 30, 2000

Natural gas sales revenue for the six months ended June 30, 2000 was down
$86,103 (11%) from the prior year due to lower gas production. Gas production
for the six months ended June 30, 2000 was 275,979 Mcf, down from 415,147 Mcf
in the prior year. The decrease in gas production results primarily from
normal well declines. Natural gas prices for the six months ended June 30,
2000 increased by $.69/Mcf to $2.76/Mcf.

QUARTER ENDED JUNE 30, 2000

Natural gas sales revenue for the quarter ended June 30, 2000 was down
$18,116 (5%) from the prior year's second quarter due to lower gas
production. Gas production for the quarter ended June 30, 2000 was 134,924
Mcf, down from 190,533 Mcf in the prior year's second quarter. The decrease
in gas production results primarily from normal well declines. Natural gas
prices for the quarter ended June 30, 2000 increased by $.72/Mcf to $2.85/Mcf.

FINANCIAL CONDITION

LIQUIDITY

The decrease in cash provided by operating activities and distributions to
partners during the six months ended June 30, 2000 results primarily from
lower cash received from sales of natural gas. The Partnership's working
capital decreased from $297,913 at December 31, 1999 to $279,780 at June 30,
2000. The decrease is attributable to distributions to partners, higher
accounts payable and normal declines in natural gas production from the
levels at the end of 1999, which result in lower receivables in connection
with sales of gas produced.

CAPITAL RESOURCES

There were no new material commitments for capital expenditures during the
period and the Partnership does not expect any in the foreseeable future.

<PAGE>

                                   SIGNATURES


In accordance with Section 13 or 15(d) of the Exchange Act, the registrant
caused this report to be signed on its behalf by the undersigned, thereunto
duly authorized.

             Atlas-Energy for the Nineties--Public #6 Ltd.

<TABLE>
<S>                            <C>
By (Signature and Title):                      Atlas Resources, Inc.,
                                               Managing General Partner

By (Signature and Title):                      /s/ James R. O'Mara
                                               James R. O'Mara
                                President, Chief Executive Officer and a Director


Date: August 14, 2000


In Accordance with the Exchange Act, this report has been signed by the
following persons on behalf of the registrant and in the capacities and on
the dates indicated.

By (Signature and Title):                      /s/ James R. O'Mara
                                               James R. O'Mara
                                President, Chief Executive Officer and a Director


Date: August 14, 2000


By (Signature and Title):                      /S/ Tony C. Banks
                                               Tony C. Banks
                                   Vice President and Chief Financial Officer


Date: August 14, 2000
</TABLE>