<PAGE>

                                   FORM 10-Q

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549



(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, 2000
[ ]     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:  0-13193


                           CABLE TV FUND 12-A, LTD.
--------------------------------------------------------------------------------
               Exact name of registrant as specified in charter

Colorado                                                             #84-0968104
--------------------------------------------------------------------------------
State of organization                                     I.R.S. employer I.D. #

                            c/o Comcast Corporation
                1500 Market Street, Philadelphia, PA 19102-2148
                -----------------------------------------------
                     Address of principal executive office

                                (215) 665-1700
                         -----------------------------
                         Registrant's telephone number


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 _____
    -----
<PAGE>

                           CABLE TV FUND 12-A, LTD.
                           ------------------------
                            (A Limited Partnership)

                           UNAUDITED BALANCE SHEETS
                           ------------------------

<TABLE>
<CAPTION>

                                                                        March 31,                December 31,
                              ASSETS                                       2000                      1999
                              ------                                -------------------       -------------------
<S>                                                                 <C>                       <C>
Cash                                                                $        2,725,686        $        2,725,686
                                                                    -------------------       -------------------

          Total assets                                              $        2,725,686        $        2,725,686
                                                                    ===================       ===================


                 LIABILITIES AND PARTNERS' CAPITAL
                 ---------------------------------

LIABILITIES:
  Advances from affiliates                                          $        2,250,184        $        2,218,699
                                                                    -------------------       -------------------

          Total liabilities                                                  2,250,184                 2,218,699
                                                                    -------------------       -------------------

PARTNER'S CAPITAL:
  General Partner-
     Contributed capital                                                         1,000                     1,000
     Distributions                                                         (29,514,625)              (29,514,625)
     Accumulated earnings                                                   29,632,501                29,640,372
                                                                    -------------------       -------------------

                                                                               118,876                   126,747
                                                                    -------------------       -------------------

Limited Partners-
  Net contributed capital (104,000 units outstanding
    at March 31, 2000 and December 31, 1999)                                44,619,655                44,619,655
  Distributions                                                           (140,543,875)             (140,543,875)
  Accumulated earnings                                                      96,280,846                96,304,460
                                                                    -------------------       -------------------

                                                                               356,626                   380,240
                                                                    -------------------       -------------------

          Total liabilities and partners' capital                   $        2,725,686        $        2,725,686
                                                                    ===================       ===================
</TABLE>

           The accompanying notes to unaudited financial statements
            are an integral part of these unaudited balance sheets.

                                       2
<PAGE>

                           CABLE TV FUND 12-A, LTD.
                           ------------------------
                            (A Limited Partnership)

                      UNAUDITED STATEMENTS OF OPERATIONS
                      ----------------------------------

<TABLE>
<CAPTION>
                                                                              For the Three Months Ended
                                                                                       March 31,
                                                                    ---------------------------------------------

                                                                           2000                      1999
                                                                    -------------------       -------------------
<S>                                                                 <C>                       <C>
OTHER INCOME (EXPENSE):
  Interest expense                                                  $                -        $          (29,012)
  Interest income                                                                    -                    44,185
  Other, net                                                                   (31,485)                 (751,916)
                                                                    -------------------       -------------------

          Total other income (expense), net                                    (31,485)                 (736,743)
                                                                    -------------------       -------------------

NET LOSS                                                            $          (31,485)       $         (736,743)
                                                                    ===================       ===================

ALLOCATION OF NET LOSS:
  General Partner                                                   $           (7,871)       $           (7,367)
                                                                    ===================       ===================

  Limited Partners                                                  $          (23,614)       $         (729,376)
                                                                    ===================       ===================

NET LOSS PER LIMITED PARTNERSHIP UNIT                               $            (0.23)       $            (7.01)
                                                                    ===================       ===================

WEIGHTED AVERAGE NUMBER OF LIMITED
  PARTNERSHIP UNITS OUTSTANDING                                                104,000                   104,000
                                                                    ===================       ===================
</TABLE>

           The accompanying notes to unaudited financial statements
              are an integral part of these unaudited statements.

                                       3
<PAGE>

                           CABLE TV FUND 12-A, LTD.
                           ------------------------
                            (A Limited Partnership)

                      UNAUDITED STATEMENTS OF CASH FLOWS
                      ----------------------------------

<TABLE>
<CAPTION>
                                                                              For the Three Months Ended
                                                                                      March 31,
                                                                    ---------------------------------------------

                                                                           2000                      1999
                                                                    -------------------       -------------------
<S>                                                                 <C>                       <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
  Net loss                                                          $          (31,485)       $         (736,743)
  Adjustments to reconcile net loss to net cash
    provided by operating activities:
          Increase in proceeds from sale in escrow                                   -                   (39,060)
          Increase in accounts payable and
            accrued liabilities and subscriber prepayments                           -                   438,973
          Increase in advances from affiliates                                  31,485                   336,830
                                                                    -------------------       -------------------

          Net cash provided by operating activities                                  -                         -
                                                                    -------------------       -------------------

Net change in cash                                                                   -                         -

Cash, beginning of period                                                    2,725,686                         -
                                                                    -------------------       -------------------

Cash, end of period                                                 $        2,725,686        $                -
                                                                    ===================       ===================

SUPPLEMENTAL CASH FLOW DISCLOSURE:
  Interest paid                                                     $                -        $                -
                                                                    ===================       ===================
</TABLE>

           The accompanying notes to unaudited financial statements
              are an integral part of these unaudited statements.

                                       4
<PAGE>

                           CABLE TV FUND 12-A, LTD.
                           ------------------------
                            (A Limited Partnership)

                    NOTES TO UNAUDITED FINANCIAL STATEMENTS
                    ---------------------------------------


(1)  This Form 10-Q is being filed in conformity with the SEC requirements for
unaudited financial statements and does not contain all of the necessary
footnote disclosures required for a complete presentation of the Balance Sheets
and Statements of Operations and Cash Flows in conformity with generally
accepted accounting principles. However, in the opinion of management, this data
includes all adjustments, consisting only of normal recurring accruals,
necessary to present fairly the financial position of Cable TV Fund 12-A, Ltd.
(the "Partnership") at March 31, 2000 and December 31, 1999 and its Statements
of Operations and Cash Flows for the three month periods ended March 31, 2000
and 1999. Certain prior year amounts were reclassified to conform to the 2000
presentation.

     The Partnership has sold all of its cable television systems. The
Partnership will not be dissolved until after the pending litigation in which
the Partnership is a named defendant has been resolved and terminated.

     On April 7, 1999, Comcast Corporation ("Comcast") completed the acquisition
of a controlling interest in Jones Intercable, Inc. ("Jones Intercable"), the
Partnership's general partner until March 2, 2000. In December 1999, Comcast and
Jones Intercable entered into a definitive merger agreement pursuant to which
Comcast agreed to acquire all of the outstanding shares of Jones Intercable not
yet owned by Comcast. On March 2, 2000, Jones Intercable was merged with and
into Comcast JOIN Holdings, Inc., a wholly owned subsidiary of Comcast. Comcast
JOIN Holdings, Inc. continues as the surviving corporation of the merger. As a
result of this transaction, Jones Intercable no longer exists and Comcast JOIN
Holdings, Inc. is now the general partner of the Partnership. References in
these Notes to "the General Partner" refer to Comcast JOIN Holdings, Inc. The
General Partner shares corporate offices with Comcast at 1500 Market Street,
Philadelphia, Pennsylvania 19102-2148.

(2)  The Partnership reimburses its general partner for certain administrative
expenses. These expenses represent the salaries and related benefits paid for
corporate personnel. Such personnel provide administrative, accounting, tax,
legal and investor relations services to the Partnership. Such services, and
their related costs, are necessary to the administration of the Partnership
until the Partnership is dissolved. Such costs were charged to other expense on
the Statements of Operations. Reimbursements by the Partnership to its general
partner for administrative expenses for the three month periods ended March 31,
2000 and 1999 were $20,070 and $11,414, respectively.

                                       5
<PAGE>

                           CABLE TV FUND 12-A, LTD.
                           ------------------------
                            (A Limited Partnership)

        MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND
        ---------------------------------------------------------------
                             RESULTS OF OPERATIONS
                             ---------------------


FINANCIAL CONDITION
-------------------

     The Partnership has sold all of its cable television systems. The
Partnership will be dissolved after the pending litigation in which the
Partnership is a named defendant has been resolved and terminated. In April
2000, the Partnership used its cash on hand to repay advances from affiliates,
leaving the Partnership with approximately $500,000 to fund its future
obligations.

RESULTS OF OPERATIONS
---------------------

     The Partnership has sold all of its cable television systems. Other expense
of $31,485 incurred in the first quarter of 2000 related to various costs
associated with the administration of the Partnership.

                                       6
<PAGE>

                          Part II - OTHER INFORMATION


Item 6. Exhibits and Reports on Form 8-K.

        a)  Exhibits

            27)  Financial Data Schedule

        b)  Reports on Form 8-K

            None

                                       7
<PAGE>

                                  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.


                                        CABLE TV FUND 12-A, LTD.
                                        BY:  COMCAST JOIN HOLDINGS, INC.
                                             General Partner



                                        By:  /S/ Lawrence J. Salva
                                             -----------------------------------
                                             Lawrence J. Salva
                                             Senior Vice President
                                             (Principal Accounting Officer)






Dated:  May 15, 2000

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