<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 September 30, 1999.
[_]      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>


                                                                     September 30,  December 31,
                     ASSETS                                              1999           1998
                     ------                                          -------------  ------------
<S>                                                                 <C>            <C>

Proceeds from sale in interest-bearing escrow account                $   2,701,650  $  2,604,000
                                                                     -------------  ------------
                  Total assets                                       $   2,701,650  $  2,604,000
                                                                     =============  ============

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

LIABILITIES:
  Accounts payable and accrued liabilities                           $   2,171,796  $    582,822
                                                                     -------------  ------------
                  Total liabilities                                      2,171,796       582,822
                                                                     -------------  ------------
PARTNERS' CAPITAL:
  General Partner-
    Contributed capital                                                      1,000         1,000
    Distributions                                                      (29,514,625)  (29,514,625)
    Accumulated earnings                                                29,646,089    30,018,919
                                                                     -------------  ------------

                                                                           132,464       505,294
                                                                     -------------  ------------
  Limited Partners-
    Net contributed capital (104,000 units outstanding
     at September 30, 1999 and December 31, 1998)                       44,619,655    44,619,655
    Distributions                                                     (140,543,875) (140,543,875)
    Accumulated earnings                                                96,321,610    97,440,104
                                                                     -------------  ------------

                                                                           397,390     1,515,884
                                                                     -------------  ------------

                  Total liabilities and partners' capital            $   2,701,650  $  2,604,000
                                                                     =============  ============
</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     For the Nine Months Ended
                                                        September 30,                  September 30,
                                                  --------------------------     ---------------------------
                                                      1999         1998              1999          1998
                                                  -----------   ------------     -----------   -------------
<S>                                              <C>           <C>              <C>           <C>
REVENUES                                          $     -       $  5,927,227     $     -       $  25,912,544

COSTS AND EXPENSES:
 Operating expenses                                     -          3,786,381           -          14,780,568
 Management fees and allocated overhead
  from General Partner                                  -            630,768           -           2,803,519
 Depreciation and amortization                          -          1,084,242           -           4,748,712
                                                  -----------   ------------     -----------   -------------

OPERATING INCOME                                        -            425,836           -           3,579,745
                                                  -----------   ------------     -----------   -------------

OTHER INCOME (EXPENSE):
 Interest expense                                     (36,918)      (357,811)       (106,731)     (1,177,625)
 Interest income on escrowed proceeds                  29,295          -              87,885         -
 Gain on sale of cable television system                -         90,423,474           -          90,423,474
 Other, net                                            (7,699)       890,952      (1,472,478)        522,865
                                                  -----------   ------------     -----------   -------------
   Total other income
    (expense), net                                    (15,322)    90,956,615      (1,491,324)     89,768,714
                                                  -----------   ------------     -----------   -------------

NET INCOME (LOSS)                                 $   (15,322)  $ 91,382,451     $(1,491,324)  $  93,348,459
                                                  ===========   ============     ===========   =============
ALLOCATION OF NET INCOME (LOSS):
 General Partner                                  $  (358,070)  $ 12,465,343     $  (372,830)  $  12,485,003
                                                  ===========   ============     ===========   =============

 Limited Partners                                 $   342,748   $ 78,917,108     $(1,118,494)  $  80,863,456
                                                  ===========   ============     ===========   =============
NET INCOME (LOSS) PER LIMITED
 PARTNERSHIP UNIT                                 $      3.30   $     758.82     $    (10.75)  $      777.53
                                                  ===========   ============     ===========   =============
WEIGHTED AVERAGE NUMBER
 OF LIMITED PARTNERSHIP
 UNITS OUTSTANDING                                    104,000        104,000         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 Nine Months Ended
                                                                        September 30,
                                                          ---------------------------------------
                                                              1999                      1998
                                                          -----------               -------------
<S>                                                       <C>                       <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
 Net income (loss)                                        $(1,491,324)              $  93,348,459
 Adjustments to reconcile net income (loss) to net
  cash provided by operating activities:
   Depreciation and amortization                                -                       4,748,712
   Gain on sale of cable television system                      -                     (90,423,474)
   Decrease  in trade receivables                               -                       1,045,587
   Increase in deposits, prepaid expenses and
    deferred charges                                          (97,650)                 (1,044,883)
   Increase (decrease) in accounts payable and accrued
    liabilities and subscriber prepayments                  1,588,974                    (869,162)
                                                          -----------               -------------
     Net cash provided by operating activities                  -                       6,805,239
                                                          -----------               -------------
CASH FLOWS FROM INVESTING ACTIVITIES:
 Purchase of property and equipment, net                        -                      (4,022,172)
 Proceeds from sale of cable television system, net of
  brokerage fees                                                -                     107,250,000
                                                          -----------               -------------
     Net cash provided by investing activities                  -                     103,227,828
                                                          -----------               -------------
CASH FLOWS FROM FINANCING ACTIVITIES:
 Proceeds from borrowings                                       -                          12,225
 Repayment of debt                                              -                      (3,308,020)
 Distribution to General Partner                                -                     (13,713,600)
 Distribution to limited partners                               -                     (93,140,800)
                                                          -----------               -------------
     Net cash used in financing activities                      -                    (110,150,195)
                                                          -----------               -------------
Decrease in cash                                                -                        (117,128)

Cash, beginning of period                                       -                       2,047,098
                                                          -----------               -------------
Cash, end of period                                       $     -                   $   1,929,970
                                                          ===========               =============
SUPPLEMENTAL CASH FLOW DISCLOSURE:
 Interest paid                                            $     -                   $   1,179,415
                                                          ===========               =============
</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 September 30, 1999 and December 31, 1998 and its
Statements of Operations for the three and nine month periods ended September
30, 1999 and 1998 and its Statements of Cash Flows for the nine month periods
ended September 30, 1999 and 1998.

     The Partnership owned and operated the cable television systems serving
areas in and around Fort Myers, Florida, until their sale in July 1998. The
Partnership also owned and operated the cable television systems serving areas
in and around Lake County, Illinois (the "Lake County System") and Orland Park
and Park Forest, Illinois (the "Orland Park System"), until their sale in
December 1998. Jones Intercable, Inc., a publicly held Colorado corporation, is
the "General Partner" and manages the Partnership.

     On April 7, 1999, Comcast Corporation ("Comcast") completed the acquisition
of a controlling interest in the General Partner for aggregate consideration of
$706.3 million. Comcast acquired an additional 1.0 million shares of the General
Partner's Class A Common Stock on June 29, 1999 for $50.0 million in a private
transaction. Upon completion of these transactions, Comcast owns approximately
13.8 million shares of the General Partner's Class A Common Stock and
approximately 2.9 million shares of the General Partner's Common Stock,
representing 39.6% of the economic interest and 48.3% of the voting interest in
the General Partner. Comcast has contributed its shares in the General Partner
to its wholly owned subsidiary, Comcast Cable Communications, Inc. ("Comcast
Cable"). The approximately 2.9 million shares of Common Stock owned by Comcast
Cable represent shares having the right to elect approximately 75% of the Board
of Directors of the General Partner. The General Partner is now a consolidated
public company subsidiary of Comcast Cable.

     In connection with Comcast's acquisition of a controlling interest in the
General Partner on April 7, 1999, all of the persons who were executive officers
of the General Partner as of that date terminated their employment with the
General Partner. The General Partner's Board of Directors has elected new
executive officers, each of whom also is an officer of Comcast. As of July 7,
1999, all persons who were employed at the General Partner's former corporate
offices in Englewood, Colorado had terminated their employment with the General
Partner. The General Partner's corporate offices are now located at 1500 Market
Street, Philadelphia, Pennsylvania 19102-2148.

(2)  On December 4, 1998, the Partnership sold the Lake County System and the
Orland Park System, its only remaining operating assets, to an unaffiliated
party for an aggregate sales price of $86,000,000. The Partnership repaid all of
its indebtedness, paid a brokerage fee to The Intercable Group, Ltd., a
subsidiary of the General Partner, settled working capital and other closing
adjustments, deposited $2,604,000 into an indemnity escrow account and
distributed the remaining net sale proceeds to its partners.

     The $2,604,000 of the sale proceeds placed in the interest-bearing
indemnity escrow account will remain in escrow until November 15, 1999 as
security for the Partnership's agreement to indemnify the buyer under the asset
purchase agreement. The Partnership's primary exposure, if any, will relate to
the representations and warranties made about the Lake County System and the
Orland Park System in the asset purchase agreement. Any amounts remaining from
this indemnity escrow account and not claimed by the buyer at the end of the
escrow period plus interest earned on the escrowed funds will be returned to the
Partnership. From this amount, the Partnership will pay its remaining
liabilities, which totaled $2,171,796 at September 30, 1999, and it will retain
the balance to cover the administrative expenses of the Partnership. Although
the sale of the Lake County System and the Orland Park System represented the
sale of the only remaining operating assets of the Partnership, the Partnership
will not be dissolved until after the pending litigation in which the
Partnership is a named defendant has been resolved and terminated.

                                       5
</PAGE>
<PAGE>

(3)  The General Partner manages the Partnership and received a fee for its
services equal to 5 percent of the gross revenues of the Partnership, excluding
revenues from the sale of cable television systems or franchises. The General
Partner has not received and will not receive a management fee after December 4,
1998. Management fees for the three and nine month periods ended September 30,
1998 were $296,361 and $1,295,627, respectively.

     The Partnership will continue to reimburse the 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
operating costs during the periods that the Partnership operated its cable
television systems. Subsequent to the sale of the Partnership's final cable
television system, such costs were charged to other expense. Reimbursements by
the Partnership to the General Partner for overhead and administrative expenses
for the three and nine month periods ended September 30, 1999 were $8,185 and
$34,140, respectively, compared to $334,407 and $1,507,892, respectively, for
the similar 1998 periods.

                                       6
<PAGE>

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

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

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

     On December 4, 1998, the Partnership sold the Lake County System and the
Orland Park System, its only remaining operating assets, to an unaffiliated
party for an aggregate sales price of $86,000,000. The Partnership repaid all of
its indebtedness, paid a brokerage fee to The Intercable Group, Ltd., settled
working capital adjustments, deposited $2,604,000 into an indemnity escrow
account and distributed the remaining net sale proceeds to its partners.

     The $2,604,000 of the sale proceeds placed in the interest-bearing
indemnity escrow account will remain in escrow until November 15, 1999 as
security for the Partnership's agreement to indemnify the buyer under the asset
purchase agreement. The Partnership's primary exposure, if any, will relate to
the representations and warranties made about the Lake County System and the
Orland Park System in the asset purchase agreement. Any amounts remaining from
this indemnity escrow account and not claimed by the buyer at the end of the
escrow period plus interest earned on the escrowed funds will be returned to the
Partnership. From this amount, the Partnership will pay its remaining
liabilities, which totaled $2,171,796 at September 30, 1999 and it will retain
the balance to cover the administrative expenses of the Partnership. Although
the sale of the Lake County System and the Orland Park System represented the
sale of the only remaining operating assets of the Partnership, the Partnership
will not be dissolved until after the pending litigation in which the
Partnership is a named defendant has been resolved and terminated.

     Because the Partnership has sold all of its assets and no further
distributions are expected to be made, transfers of limited partnership
interests would have no economic or practical value. The General Partner
therefore has determined, in accordance with the authority granted to it under
Section 3.5 of the Partnership's limited partnership agreement, that it will not
process any transfers of limited partnership interests in the Partnership during
the remainder of the Partnership's term.

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

     Due to the Partnership's sale of the Orland Park System and Lake County
System on December 4, 1998, which were the Partnership's last remaining
operating assets, a discussion of results of operations would not be meaningful.
Other expense of $1,472,478 incurred in the first nine months of 1999 primarily
related to various costs associated with the sale of the Partnership's systems
and the administration of the Partnership.

                                       7
<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

                                       8
<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: JONES INTERCABLE, INC.
                                     General Partner



                                  By: /S/ Lawrence S. Smith
                                     -------------------------------------
                                     Lawrence S. Smith
                                     Principal Accounting Officer


                                  By: /S/ Joseph J. Euteneuer
                                     -------------------------------------
                                     Joseph J. Euteneuer
                                     Vice President (Authorized Officer)



Dated:  November 12, 1999

                                       9