<PAGE>

                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549
                            -------------------------

                                    FORM 8-K

                                 CURRENT REPORT

                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934

       Date of Report (or Date of Earliest Event Reported): June 26, 1998



                    SWIFT ENERGY INCOME PARTNERS 1990-C, LTD.
             (Exact name of Registrant as specified in its charter)


        TEXAS                    33-11773-14               76-0318471

(State of incorporation    (Commission File Number)       (IRS Employer
    or organization)                                    Identification No.)


                        16825 Northchase Drive, Suite 400
                              Houston, Texas 77060
                    (Address of principal executive offices)



                                 (281) 874-2700
                         (Registrant's telephone number)


<PAGE>

ITEM 2.  Disposition of Assets
         ---------------------

     Substantially  all of the assets of Swift Energy  Income  Partners  1990-C,
Ltd. (the "Partnership"), consisting of interest in real property and in oil and
gas reserves located therein,  ("Property Interests") were sold at auction as of
March 1, 1998. The bulk of the Partnership's Property Interests included partial
interest in three fields in  Schleicher  County,  Texas in the Permian  Basis of
West  Texas and one field in Wheeler  County,  Texas.  Collectively,  these four
fields accounted for  approximately  63% of the total proceeds received from the
sale  of  the  Partnership's  Property  Interests.  The  total  proceeds  to the
Partnership, net of selling expenses, were $843,350. The limited partners' share
was  $759,015.  An initial  distribution  of  proceeds  was made to the  limited
partners  on April 15,  1998,  representing  all the  assets of the  Partnership
except for  insubstantial  amounts held back for contingency  purposes.  A small
final distribution is anticipated to be made on or about June 30, 1998, at which
time the  Partnership  will  dissolve  pursuant  to the  Texas  Revised  Limited
Partnership Act.



                                    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, hereunto duly authorized person.

Dated: June 26, 1998


                        SWIFT ENERGY INCOME PARTNERS 1990-C, LTD.


                        By:  Swift Energy Company, as Managing General Partner



                              By:  ----------------------------------------
                                   Alton D. Heckaman, Jr.
                                   Vice President and Controller


                                       2
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SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549
                            -------------------------

                                    FORM 8-K

                                 CURRENT REPORT

                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934

       Date of Report (or Date of Earliest Event Reported): June 26, 1998

                    SWIFT ENERGY INCOME PARTNERS 1990-C, LTD.
             (Exact name of Registrant as specified in its charter)

        TEXAS                    33-11773-14               76-0318471

(State of incorporation    (Commission File Number)       (IRS Employer
    or organization)                                    Identification No.)

                        16825 Northchase Drive, Suite 400
                              Houston, Texas 77060
                    (Address of principal executive offices)

                                 (281) 874-2700
                         (Registrant's telephone number)
ITEM 2.  Disposition of Assets
         ---------------------

     Substantially  all of the assets of Swift Energy  Income  Partners  1990-C,
Ltd. (the "Partnership"), consisting of interest in real property and in oil and
gas reserves located therein,  ("Property Interests") were sold at auction as of
March 1, 1998. The bulk of the Partnership's Property Interests included partial
interest in three fields in  Schleicher  County,  Texas in the Permian  Basis of
West  Texas and one field in Wheeler  County,  Texas.  Collectively,  these four
fields accounted for  approximately  63% of the total proceeds received from the
sale  of  the  Partnership's  Property  Interests.  The  total  proceeds  to the
Partnership, net of selling expenses, were $843,350. The limited partners' share
was  $759,015.  An initial  distribution  of  proceeds  was made to the  limited
partners  on April 15,  1998,  representing  all the  assets of the  Partnership
except for  insubstantial  amounts held back for contingency  purposes.  A small
final distribution is anticipated to be made on or about June 30, 1998, at which
time the  Partnership  will  dissolve  pursuant  to the  Texas  Revised  Limited
Partnership Act.

                                    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, hereunto duly authorized person.

Dated: June 26, 1998

                        SWIFT ENERGY INCOME PARTNERS 1990-C, LTD.

                        By:  Swift Energy Company, as Managing General Partner

                              By:  ----------------------------------------
                                   Alton D. Heckaman, Jr.
                                   Vice President and Controller

                                       2