<PAGE>
================================================================================

                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 10-Q

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

         FOR THE QUARTERLY PERIOD ENDED:  JUNE 30, 2002

                                       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: 33-42337

                       CAPSTEAD SECURITIES CORPORATION IV
             (Exact name of Registrant as specified in its Charter)


               DELAWARE                                          75-2390594
    (State or other jurisdiction of                          (I.R.S. Employer
    incorporation or organization)                          Identification No.)

8401 NORTH CENTRAL EXPRESSWAY, SUITE 800, DALLAS, TX               75225
     (Address of principal executive offices)                   (Zip Code)

       Registrant's telephone number, including area code: (214) 874-2323

The Registrant meets the conditions set forth in General Instruction H(1)(a) and
(b) for Form 10-Q and is therefore filing this Form under the reduced disclosure
format.

Indicate by check mark whether the Registrant (1) has filed all documents and
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
                                                      ---         ---


                      APPLICABLE ONLY TO CORPORATE ISSUERS:

Indicate the number of shares outstanding of each of the issuer's classes of
common stock, as of the last practicable date.



Common Stock ($1.00 par value)                      1,000 as of August 12, 2002


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



<PAGE>
                       CAPSTEAD SECURITIES CORPORATION IV
                                    FORM 10-Q
                       FOR THE QUARTER ENDED JUNE 30, 2002


                                      INDEX



<Table>
<Caption>
                                                                                                            PAGE
                                                                                                            ----
<S>                                                                                                         <C>
                                       PART I. -- FINANCIAL INFORMATION

ITEM 1. Financial Statements

   Balance Sheets -- June 30, 2002 and December 31, 2001..................................................   1

   Statements of Operations -- Quarter and Six Months Ended
     June 30, 2002 and 2001...............................................................................   2

   Statements of Cash Flows -- Six Months Ended
     June 30, 2002 and 2001...............................................................................   3

   Notes to Financial Statements..........................................................................   4

ITEM 2. Management's Discussion and Analysis of
          Financial Condition and Results of Operations...................................................   6


                                        PART II. -- OTHER INFORMATION

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

SIGNATURES................................................................................................   7
</Table>




<PAGE>



ITEM 1. FINANCIAL STATEMENTS


                        PART I. -- FINANCIAL INFORMATION
                       CAPSTEAD SECURITIES CORPORATION IV
                                 BALANCE SHEETS
                      (IN THOUSANDS, EXCEPT PER SHARE DATA)



<Table>
<Caption>
                                                            JUNE 30, 2002    DECEMBER 31, 2001
                                                           ---------------   -----------------
                                                             (UNAUDITED)
<S>                                                        <C>               <C>
ASSETS
   Mortgage securities collateral                          $        50,896    $        72,309
   Cash and cash equivalents                                            14                 14
                                                           ---------------    ---------------

                                                           $        50,910    $        72,323
                                                           ===============    ===============

LIABILITIES
   Collateralized mortgage securities                      $        50,255    $        71,402
                                                           ---------------    ---------------

STOCKHOLDER'S EQUITY
   Common stock - $1.00 par value,
     1 shares authorized,
     issued and outstanding                                              1                  1
   Paid-in capital                                                      24                 18
   Undistributed loss                                                   (5)                --
   Accumulated other comprehensive
     income                                                            635                902
                                                           ---------------    ---------------
                                                                       655                921
                                                           ---------------    ---------------
                                                           $        50,910    $        72,323
                                                           ===============    ===============
</Table>








See accompanying notes to financial statements.


                                      -1-
<PAGE>


                       CAPSTEAD SECURITIES CORPORATION IV
                            STATEMENTS OF OPERATIONS
                                 (IN THOUSANDS)
                                   (UNAUDITED)



<Table>
<Caption>
                                                         QUARTER ENDED                 SIX MONTHS ENDED
                                                           JUNE 30                         JUNE 30
                                                ----------------------------    ----------------------------
                                                    2002            2001            2002            2001
                                                ------------    ------------    ------------    ------------
<S>                                             <C>             <C>             <C>             <C>
Interest income:
   Mortgage securities collateral               $        822    $      2,351    $      1,781    $      5,163
   Receivable from (payable to) parent                    --              --              (2)              1
                                                ------------    ------------    ------------    ------------

       Total interest income                             822           2,351           1,779           5,164
                                                ------------    ------------    ------------    ------------

Interest expenses on collateralized
   mortgage securities                                   777           2,280           1,683           5,002
                                                ------------    ------------    ------------    ------------

         Net interest income                              45              71              96             162
                                                ------------    ------------    ------------    ------------

Other operating expense:
   Management fee                                          2               2               5               5
   Professional fee and other                              1               1               1              11
   Pool insurance                                         45              88              97             186
                                                ------------    ------------    ------------    ------------

       Total other operating expense                      48              91             103             202
                                                ------------    ------------    ------------    ------------

Net loss                                                  (3)            (20)             (7)            (40)
                                                ------------    ------------    ------------    ------------

Other comprehensive income (loss)                       (110)             25            (267)           (623)
                                                ------------    ------------    ------------    ------------

Comprehensive income (loss)                     $       (113)   $          5    $       (274)   $       (663)
                                                ============    ============    ============    ============
</Table>




See accompanying notes to financial statements.



                                      -2-
<PAGE>


                       CAPSTEAD SECURITIES CORPORATION IV
                            STATEMENTS OF CASH FLOWS
                                 (IN THOUSANDS)
                                   (UNAUDITED)



<Table>
<Caption>
                                                                       SIX MONTHS ENDED JUNE 30
                                                                    ------------------------------
                                                                        2002             2001
                                                                    -------------    -------------
<S>                                                                 <C>              <C>
OPERATING ACTIVITIES:
   Net loss                                                         $          (7)   $         (40)
   Noncash item - amortization of
     discount and premium                                                    (125)               8
   Net change in other assets and accrued expenses                             --              (70)
                                                                    -------------    -------------

     Net cash used in operating activities                                   (132)            (102)
                                                                    -------------    -------------

INVESTING ACTIVITIES:
   Mortgage securities collateral:
     Principal collections on collateral                                   20,561           22,012
     Decrease in accrued interest receivable                                  133              151
     Increase in short-term investments                                        --             (269)
                                                                    -------------    -------------

       Net cash provided by investing activities                           20,694           21,894
                                                                    -------------    -------------

FINANCING ACTIVITIES:
   Collateralized mortgage securities:
     Principal payments on securities                                     (20,561)         (21,736)
     Decrease in accrued interest payable                                      (9)            (104)
   Capital contributions (distributions)                                        8              (40)
                                                                    -------------    -------------

       Net cash used in financing activities                              (20,562)         (21,880)
                                                                    -------------    -------------

Net change in cash and cash equivalents                                        --              (88)

Cash and cash equivalents at beginning
   of period                                                                   14              120
                                                                    -------------    -------------
Cash and cash equivalents at end of
   period                                                           $          14    $          32
                                                                    =============    =============
</Table>




See accompanying notes to financial statements.




                                      -3-
<PAGE>


                       CAPSTEAD SECURITIES CORPORATION IV
                          NOTES TO FINANCIAL STATEMENTS
                                  JUNE 30, 2002
                                   (UNAUDITED)


NOTE A -- BASIS OF PRESENTATION

The accompanying unaudited financial statements have been prepared in accordance
with generally accepted accounting principles for interim financial information
and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X.
Accordingly, they do not include all of the information and footnotes required
by generally accepted accounting principles for complete financial statements.
In the opinion of management, all adjustments (consisting of normal recurring
accruals) considered necessary for a fair presentation have been included.
Operating results for the quarter and six months ended June 30, 2002 are not
necessarily indicative of the results that may be expected for the calendar year
ending December 31, 2002. For further information refer to the financial
statements and footnotes thereto included in the Capstead Securities Corporation
IV (the "Company") annual report on Form 10-K for the year ended December 31,
2001.

NOTE B -- DISCLOSURES REGARDING FAIR VALUES OF MORTGAGE SECURITIES COLLATERAL

The estimated fair values of mortgage securities collateral have been determined
using available market information and appropriate valuation methodologies.
However, considerable judgment is required in interpreting market data to
develop these estimates. In addition, fair values fluctuate on a daily basis.
Accordingly, estimates presented herein are not necessarily indicative of the
amounts that could be realized in a current market exchange. The use of
different market assumptions and/or estimation methodologies may have a material
effect on estimated fair value amounts.

Fair values are estimated using quoted market prices, when available, including
quotes made by Capstead Mortgage Corporation's lenders in connection with
designating collateral for repurchase arrangements.

The following summarizes fair value disclosures for mortgage securities
collateral held available-for-sale for the periods indicated (in thousands):


<Table>
<Caption>
                                                            JUNE 30, 2002   DECEMBER 31, 2001
                                                           ---------------  -----------------
<S>                                                        <C>               <C>
Carrying amount                                            $        50,261   $        71,407
Unrealized gains                                                       635               902
                                                           ---------------   ---------------
  Fair value                                               $        50,896   $        72,309
                                                           ===============   ===============
</Table>



                                      -4-
<PAGE>


The maturity of mortgage securities collateral is directly affected by the rate
of principal prepayments by mortgagors. In addition, upon redemption of
remaining bonds outstanding pursuant to clean-up calls, released collateral may
be sold provided the collateral has paid down to within 15% of its original
issue amount. Such sales are deemed maturities under the provisions of Statement
of Financial Accounting Standards No. 115. There was no collateral released
during the first six months of 2002 or 2001.

NOTE C -- NET INTEREST INCOME ANALYSIS

The following summarizes interest income and interest expense and the average
effective interest rates (dollars in thousands):


<Table>
<Caption>
                                                                              QUARTER ENDED JUNE 30
                                                          ----------------------------------------------------------
                                                                     2002                           2001
                                                          ---------------------------    ---------------------------
                                                                           AVERAGE                        AVERAGE
                                                             AMOUNT          RATE           AMOUNT          RATE
                                                          ------------   ------------    ------------   ------------
<S>                                                       <C>            <C>             <C>            <C>
Interest income on mortgage
   securities collateral                                  $        822           6.05%   $      2,351           7.21%
Interest expense on
   collateralized mortgage securities                              777           5.68           2,280           7.00
                                                          ------------                   ------------
                                                          $         45                   $         71
                                                          ============                   ============
</Table>

<Table>
<Caption>
                                                                            SIX MONTHS ENDED JUNE 30
                                                          ----------------------------------------------------------
                                                                     2002                           2001
                                                          ---------------------------    ---------------------------
                                                                           AVERAGE                        AVERAGE
                                                             AMOUNT          RATE           AMOUNT          RATE
                                                          ------------   ------------    ------------   ------------
<S>                                                       <C>            <C>             <C>            <C>
Interest income on mortgage
   securities collateral                                  $      1,781           5.99%   $      5,163           7.60%
Interest expense on
   collateralized mortgage securities                            1,683           5.63           5,002           7.37
                                                          ------------                   ------------
                                                          $         98                   $        161
                                                          ============                   ============
</Table>


Changes in interest income and interest expense due to changes in interest rates
versus changes in volume were as follows (in thousands):


<Table>
<Caption>
                                                                       QUARTER ENDED JUNE 30, 2002
                                                           -----------------------------------------------
                                                               RATE*           VOLUME*           TOTAL
                                                           -------------    -------------    -------------
<S>                                                        <C>              <C>              <C>
Interest income on mortgage
   securities collateral                                   $        (332)   $      (1,197)   $      (1,529)
Interest expense on collateralized
   mortgage securities                                              (368)          (1,135)          (1,503)
                                                           -------------    -------------    -------------
                                                           $          36    $         (62)   $         (26)
                                                           =============    =============    =============
</Table>

<Table>
<Caption>
                                                                    SIX MONTHS ENDED JUNE 30, 2002
                                                           -----------------------------------------------
                                                               RATE*            VOLUME*           TOTAL
                                                           -------------    -------------    -------------
<S>                                                        <C>              <C>              <C>
Interest income on mortgage
   securities collateral                                   $        (923)   $      (2,459)   $      (3,382)
Interest expense on collateralized
   mortgage securities                                              (983)          (2,336)          (3,319)
                                                           -------------    -------------    -------------
                                                           $          60    $        (123)   $         (63)
                                                           =============    =============    =============
</Table>


*        The change in interest due to both volume and rate has been allocated
         to volume and rate changes in proportion to the relationship of the
         absolute dollar amounts of the change in each.


                                      -5-
<PAGE>


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


Capstead Securities Corporation IV (the "Company") was incorporated on August
16, 1991, as a special-purpose finance subsidiary of Capstead Mortgage
Corporation ("CMC") and commenced operations on December 23, 1991 with the
issuance of its first collateralized mortgage obligation ("CMO"), Series
1991-VIII. As of June 30, 2002, the Company had issued 19 CMOs with an aggregate
initial principal balance of $4,572,644,000, including two CMOs with an
aggregate initial principal balance of $551,537,000, which were recorded as
sales when issued in 1992. The Company has not issued any CMOs since September
30, 1998.

The Company's net losses are due to operational costs incurred (management and
administrative fees). Other comprehensive loss reflects the decline in pledged
CMO collateral since year-end as a result of relatively high mortgage
prepayments. As the underlying mortgages pay off, related unrealized gains are
eliminated.


LIQUIDITY AND CAPITAL RESOURCES

All ongoing cash CMO expenses of the Company are paid out of the excess cash
flow on the CMO issued before the residual holders receive their residual
interest. The Company believes that the excess cash flows will be sufficient to
pay ongoing CMO expenses. Cash flow requirements due to ongoing operational
costs are funded by CMC.


                          PART II. -- OTHER INFORMATION


ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K:

(a)      Exhibits: The following Exhibit is presented herewith:

         Exhibit 99.1 - Certification pursuant to Section 906 of the
         Sarbanes-Oxley Act of 2002.

(b)      Reports on Form 8-K: None






                                      -6-
<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.

                                           CAPSTEAD SECURITIES CORPORATION IV


Date:  August 12, 2002                     By:   /s/ ANDREW F. JACOBS
                                              ---------------------------------
                                              Andrew F. Jacobs
                                              Chairman, Chief Executive Officer
                                              and President


Date:  August 12, 2002                     By:   /s/ PHILLIP A. REINSCH
                                              ---------------------------------
                                              Phillip A. Reinsch
                                              Senior Vice President - Control




                                      -7-
<PAGE>

                               INDEX TO EXHIBITS


<Table>
<Caption>
EXHIBIT
NUMBER           DESCRIPTION
-------          -----------
<S>              <C>
 99.1            Certification pursuant to Section 906 of the Sarbanes-Oxley
                 Act of 2002.
</Table>