<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: SEPTEMBER 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 November 11, 2002

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


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


                                      INDEX

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

ITEM 1.       Financial Statements

<S>                                                                                                        <C>
   Balance Sheets -- September 30, 2002 and December 31, 2001.............................................   1

   Statements of Operations -- Quarter and Nine Months Ended
     September 30, 2002 and 2001..........................................................................   2

   Statements of Cash Flows -- Nine Months Ended
     September 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

ITEM 3.       Quantitative and Qualitative Disclosure of Market Risk......................................   6

ITEM 4.       Controls and Procedures.....................................................................   6


                                   PART II. -- OTHER INFORMATION

ITEM 6.       Exhibits and Reports on Form 8-K............................................................   7

SIGNATURES................................................................................................   7

CERTIFICATIONS............................................................................................   8
</Table>


<PAGE>


ITEM 1. FINANCIAL STATEMENTS


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

<Table>
<Caption>
                                       SEPTEMBER 30, 2002     DECEMBER 31, 2001
                                      ------------------      -----------------
                                          (UNAUDITED)
<S>                                    <C>                     <C>
ASSETS
   Mortgage securities collateral          $ 46,236                $ 72,309
   Cash and cash equivalents                     14                      14
                                           --------                --------

                                           $ 46,250                $ 72,323
                                           ========                ========
LIABILITIES
   Collateralized mortgage securities      $ 45,653                $ 71,402
                                           --------                --------

STOCKHOLDER'S EQUITY
   Common stock - $1.00 par value,
     1 shares authorized,
     issued and outstanding                       1                       1
   Paid-in capital                               29                      18
   Undistributed loss                           (10)                     --
   Accumulated other comprehensive
     income                                     577                     902
                                           --------                --------
                                                597                     921
                                           --------                --------
                                           $ 46,250                $ 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                    NINE MONTHS ENDED
                                                   SEPTEMBER 30                       SEPTEMBER 30
                                              -----------------------           -----------------------
                                                2002           2001              2002            2001
                                              -------         -------          -------          -------
<S>                                            <C>           <C>               <C>             <C>
Interest income:
   Mortgage securities collateral              $ 748          $ 1,838          $ 2,529          $ 7,001
   Receivable from (payable to) parent            --               --               (1)               1
                                               -----          -------          -------          -------

       Total interest income                     748            1,838            2,528            7,002
                                               -----          -------          -------          -------

Interest expenses on collateralized
   mortgage securities                           708            1,795            2,392            6,797
                                               -----          -------          -------          -------

         Net interest income                      40               43              136              205
                                               -----          -------          -------          -------

Other operating expense:
   Management fee                                  3                3                8                8
   Professional fee and other                     --                4                1               16
   Pool insurance                                 40               74              137              259
                                               -----          -------          -------          -------

       Total other operating expense              43               81              146              283
                                               -----          -------          -------          -------

Net loss                                          (3)             (38)             (10)             (78)

Other comprehensive income (loss)                (58)              33             (325)            (590)
                                               -----          -------          -------          -------

Comprehensive loss                             $ (61)         $    (5)         $  (335)         $  (668)
                                               =====          =======          =======          =======

</Table>


See accompanying notes to financial statements.



                                       2
<PAGE>


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


<Table>
<Caption>
                                                                                   NINE MONTHS ENDED
                                                                                      SEPTEMBER 30
                                                                           ----------------------------------
                                                                               2002                   2001
                                                                           ------------          ------------
<S>                                                                         <C>                 <C>
OPERATING ACTIVITIES:
   Net loss                                                                $        (10)         $        (78)
   Noncash item - amortization of
     discount and premium                                                          (148)                  (21)
   Net change in other assets and accrued expenses                                   --                   (70)
                                                                           ------------          ------------

     Net cash used in operating activities                                         (158)                 (169)
                                                                           ------------          ------------

INVESTING ACTIVITIES:
   Mortgage securities collateral:
     Principal collections on collateral                                         25,039                40,894
     Decrease in accrued interest receivable                                        157                   273
     Increase in short-term investments                                              --                  (371)
                                                                           ------------          ------------

       Net cash provided by investing activities                                 25,196                40,796
                                                                           ------------          ------------

FINANCING ACTIVITIES:
   Collateralized mortgage securities:
     Principal payments on securities                                           (25,039)              (40,503)
     Decrease in accrued interest payable                                           (10)                 (155)
   Capital contributions (distributions)                                             11                   (34)
                                                                           ------------          ------------

       Net cash used in financing activities                                    (25,038)              (40,692)
                                                                           ------------          ------------

Net change in cash and cash equivalents                                              --                   (65)

Cash and cash equivalents at beginning
   of period                                                                         14                   120
                                                                           ------------          ------------
Cash and cash equivalents at end of
   period                                                                  $         14          $         55
                                                                           ============          ============
</Table>

See accompanying notes to financial statements.



                                       3
<PAGE>


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


NOTE A -- BASIS OF PRESENTATION

The accompanying unaudited financial statements have been prepared in accordance
with generally accepted accounting principles accepted in the United States
("GAAP") 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 GAAP 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 nine months ended September 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>
                                  SEPTEMBER 30, 2002   DECEMBER 31, 2001
                                  ------------------   -----------------
<S>                                    <C>                <C>
Carrying amount                        $   45,659         $   71,407
Unrealized gains                              577                902
                                       ----------         ----------
  Fair value                           $   46,236         $   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 SEPTEMBER 30
                                                                ---------------------------------------------------
                                                                        2002                           2001
                                                                --------------------         ----------------------
                                                                             AVERAGE                        AVERAGE
                                                                 AMOUNT       RATE            AMOUNT         RATE
                                                                 ------      -------          ------        -------
<S>                                                              <C>          <C>             <C>            <C>
Interest income on mortgage
   securities collateral                                         $  748       6.37%           $1,838         6.50%
Interest expense on
   collateralized mortgage securities                               708       6.00             1,795         6.36
                                                                 ------                       ------
                                                                 $   40                       $   43
                                                                 ======                       ======
</Table>


<Table>
<Caption>
                                                                           NINE MONTHS ENDED SEPTEMBER 30
                                                                 --------------------------------------------------
                                                                        2002                          2001
                                                                 -------------------         ----------------------
                                                                             AVERAGE                        AVERAGE
                                                                 AMOUNT       RATE            AMOUNT         RATE
                                                                 ------      -------          ------        -------
<S>                                                              <C>          <C>             <C>            <C>
Interest income on mortgage
   securities collateral                                         $2,529       6.09%           $7,001         7.29%
Interest expense on
   collateralized mortgage securities                             2,392       5.72             6,797         7.09
                                                                 ------                       ------
                                                                 $  137                       $  204
                                                                 ======                       ======
</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 SEPTEMBER 30, 2002
                                                                  -----------------------------------------------
                                                                  RATE*           VOLUME*                  TOTAL
                                                                  -----           -------                 -------
<S>                                                               <C>             <C>                     <C>
Interest income on mortgage
   securities collateral                                          $ (36)          $(1,054)                $(1,090)
Interest expense on collateralized
   mortgage securities                                              (96)             (991)                 (1,087)
                                                                  -----           -------                 -------
                                                                  $  60           $   (63)                $    (3)
                                                                  =====           =======                 =======
</Table>


<Table>
<Caption>

                                                                        NINE MONTHS ENDED SEPTEMBER 30, 2002
                                                                -------------------------------------------------
                                                                 RATE*              VOLUME*                TOTAL
                                                                -------             -------               -------
<S>                                                             <C>                 <C>                   <C>
Interest income on mortgage
   securities collateral                                        $(1,009)            $(3,463)              $(4,472)
Interest expense on collateralized
   mortgage securities                                           (1,120)             (3,285)               (4,405)
                                                                -------             -------               -------
                                                                $   111             $  (178)              $   (67)
                                                                =======             =======               =======
</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 September 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.

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURE OF MARKET RISKS

The information required by this Item is incorporated by reference to the
information included in Item 2. "Management's Discussion and Analysis of
Financial Condition and Results of Operations."

ITEM 4. CONTROLS AND PROCEDURES

As of September 30, 2002, an evaluation was performed under the supervision and
with the participation of the Company's management, including the Chief
Executive Officer ("CEO") and Senior Vice President - Control ("CFO"), of the
effectiveness of the design and operation of the Company's disclosure controls
and procedures. Based on that evaluation, the Company's management, including
the CEO and CFO, concluded that the Company's disclosure controls and procedures
were effective as of September 30, 2002. There have been no significant changes
in the Company's internal controls or in other factors that could significantly
affect internal controls subsequent to September 30, 2002.




                                       6
<PAGE>


                          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



                                   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:  November 11, 2002          By:  /s/ ANDREW F. JACOBS
                                       ----------------------------------------
                                       Andrew F. Jacobs
                                       Chairman, Chief Executive Officer and
                                       President


Date:  November 11, 2002          By:  /s/ PHILLIP A. REINSCH
                                       ----------------------------------------
                                       Phillip A. Reinsch
                                       Senior Vice President - Control




                                       7
<PAGE>


                                 CERTIFICATIONS


I, Andrew F. Jacobs, certify that:

1.       I have reviewed this quarterly report on Form 10-Q of Capstead
         Securities Corporation IV;

2.       Based on my knowledge, this quarterly report does not contain any
         untrue statement of a material fact or omit to state a material fact
         necessary to make the statements made, in light of the circumstances
         under which such statements were made, not misleading with respect to
         the period covered by this quarterly report;

3.       Based on my knowledge, the financial statements, and other financial
         information included in this quarterly report, fairly present in all
         material respects the financial condition, results of operations and
         cash flows of the registrant as of, and for, the periods presented in
         this quarterly report;

4.       The registrant's other certifying officers and I are responsible for
         establishing and maintaining disclosure controls and procedures (as
         defined in Exchange Act Rules 13a-14 and 15d-14) for the registrant and
         we have:

         a)       designed such disclosure controls and procedures to ensure
                  that material information relating to the registrant,
                  including its consolidated subsidiaries, is made known to us
                  by others within those entities, particularly during the
                  period in which this quarterly report is being prepared;

         b)       evaluated the effectiveness of the registrant's disclosure
                  controls and procedures as of a date within 90 days prior to
                  the filing date of this quarterly report (the "Evaluation
                  Date"); and

         c)       presented in this quarterly report our conclusions about the
                  effectiveness of the disclosure controls and procedures based
                  on our evaluation as of the Evaluation Date;

5.       The registrant's other certifying officers and I have disclosed, based
         on our most recent evaluation, to the registrant's auditors and the
         audit committee of registrant's board of directors:

         a)       all significant deficiencies in the design or operation of
                  internal controls which could adversely affect the
                  registrant's ability to record, process, summarize and report
                  financial data and have identified for the registrant's
                  auditors any material weaknesses in internal controls; and

         b)       any fraud, whether or not material, that involves management
                  or other employees who have a significant role in the
                  registrant's internal controls; and

6.       The registrant's other certifying officers and I have indicated in this
         quarterly report whether or not there were significant changes in
         internal controls or in other factors that could significantly affect
         internal controls subsequent to the date of our most recent evaluation,
         including any corrective actions with regard to significant
         deficiencies and material weaknesses.



Date:  November 11, 2002         By:  /s/ ANDREW F. JACOBS
                                      -----------------------------------------
                                      Andrew F. Jacobs
                                      Chairman, Chief Executive Officer
                                      and President




                                       8
<PAGE>



                                 CERTIFICATIONS


I, Phillip A. Reinsch, certify that:

1.       I have reviewed this quarterly report on Form 10-Q of Capstead
         Securities Corporation IV;

2.       Based on my knowledge, this quarterly report does not contain any
         untrue statement of a material fact or omit to state a material fact
         necessary to make the statements made, in light of the circumstances
         under which such statements were made, not misleading with respect to
         the period covered by this quarterly report;

3.       Based on my knowledge, the financial statements, and other financial
         information included in this quarterly report, fairly present in all
         material respects the financial condition, results of operations and
         cash flows of the registrant as of, and for, the periods presented in
         this quarterly report;

4.       The registrant's other certifying officers and I are responsible for
         establishing and maintaining disclosure controls and procedures (as
         defined in Exchange Act Rules 13a-14 and 15d-14) for the registrant and
         we have:

         a)       designed such disclosure controls and procedures to ensure
                  that material information relating to the registrant,
                  including its consolidated subsidiaries, is made known to us
                  by others within those entities, particularly during the
                  period in which this quarterly report is being prepared;

         b)       evaluated the effectiveness of the registrant's disclosure
                  controls and procedures as of a date within 90 days prior to
                  the filing date of this quarterly report (the "Evaluation
                  Date"); and

         c)       presented in this quarterly report our conclusions about the
                  effectiveness of the disclosure controls and procedures based
                  on our evaluation as of the Evaluation Date;

5.       The registrant's other certifying officers and I have disclosed, based
         on our most recent evaluation, to the registrant's auditors and the
         audit committee of registrant's board of directors:

         a)       all significant deficiencies in the design or operation of
                  internal controls which could adversely affect the
                  registrant's ability to record, process, summarize and report
                  financial data and have identified for the registrant's
                  auditors any material weaknesses in internal controls; and

         b)       any fraud, whether or not material, that involves management
                  or other employees who have a significant role in the
                  registrant's internal controls; and

6.       The registrant's other certifying officers and I have indicated in this
         quarterly report whether or not there were significant changes in
         internal controls or in other factors that could significantly affect
         internal controls subsequent to the date of our most recent evaluation,
         including any corrective actions with regard to significant
         deficiencies and material weaknesses.



Date:  November 11, 2002         By:  /s/ PHILLIP A. REINSCH
                                     ------------------------------------------
                                     Phillip A. Reinsch
                                     Senior Vice President - Control




                                       9
<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>