<PAGE>
Filed Pursuant to Rule 424(b)(5) SEC File No. 333-26865
PROSPECTUS SUPPLEMENT
(TO PROSPECTUS DATED MAY 16, 1997)
CAPSTEAD MORTGAGE CORPORATION
144,000 SHARES
SHARES OF COMMON STOCK
(PAR VALUE OF $0.01)
10,000 SHARES
SHARES OF $1.26 CUMULATIVE CONVERTIBLE PREFERRED, SERIES B (PAR VALUE OF $.10)
----------------
Pursuant to a Sales Agency Agreement dated as of December 6, 1995 (the "Common
Stock Sales Agency Agreement") between Capstead Mortgage Corporation (the
"Company") and PaineWebber Incorporated ("PaineWebber") (as amended by Amendment
No. 1 thereto dated as of September 10, 1996 and Amendment No. 2 thereto dated
as of March 4, 1997) which has been filed as an exhibit to the Registration
Statement of which this Prospectus Supplement is a part and which is
incorporated by reference herein, the Company has sold, through PaineWebber, as
agent of the Company, 144,000 shares of the Company's common stock, par value
$.01 per share (the "Common Stock"), pursuant to ordinary brokers' transactions
on the New York Stock Exchange (the "NYSE"). Pursuant to a Sales Agency
Agreement dated as of September 17, 1996 (the "Preferred Stock Sales Agency
Agreement") between the Company and PaineWebber (as amended by Amendment No. 1
thereto dated as of March 4, 1997), which has been filed as an exhibit to the
Registration Statement of which this Prospectus Supplement is a part and which
is incorporated herein by reference, the Company has sold through PaineWebber,
as agent of the Company, 10,000 shares of the Company's $1.26 Cumulative
Convertible Preferred, Series B, par value $.10 per share (the "Series B
Preferred Stock") pursuant to ordinary brokers' transactions on the NYSE.
COMMON STOCK
Shares sold during Pricing Period..December 8, 1997 through December 12, 1997
<TABLE>
<S> <C>
4,000 Average Market Price Shares
140,000 Additional Shares
144,000 Total Shares Sold
</TABLE>
Arithmetic Mean of the High and Low Sales
Prices of the Shares reported on the NYSE
(the "Average Market Price") for each
Trading Day of the Pricing Period:
<TABLE>
<CAPTION>
AVERAGE (OR TOTAL)
12/8/97 12/9/97 12/10/97 12/11/97 12/12/97 FOR PRICING PERIOD
--------- --------- --------- --------- --------- ------------------
<S> <C> <C> <C> <C> <C>
$ 0.0000 $23.8125 $23.1875 $22.2813 $22.2500 $22.8828
</TABLE>
<TABLE>
<S> <C> <C>
High and Low Sales Prices at
which Average Market Shares
were sold during pricing
period...................... $24.0000 $22.3125
</TABLE>
Average Market Price Shares:
<TABLE>
<S> <C>
Gross Proceeds to Company...................................... $ 91,531.25
2% Discount.................................................... $ 1,830.63
-------------
Net Proceeds to Company........................................ $ 89,700.62
Gross Sales Proceeds........................................... $ 92,162.50
Compensation to Agent.......................................... $ 2,461.88
-------------
Net Proceeds to Company........................................ $ 89,700.62
</TABLE>
<TABLE>
<S> <C>
Additional Shares Sold:
Gross Proceeds to Company...................................... $3,172,312.50
Commission to Agent............................................ $ 63,446.26
-------------
Net Proceeds to Company........................................ $3,108,866.24
Total Net Proceeds to Company ................................. $3,198,566.86
Total Compensation to Agent.................................... $ 65,908.14
</TABLE>
On December 12, 1997, the last reported sales price of the Shares on
the NYSE was........................................................ $22.1250
<PAGE>
SERIES B PREFERRED STOCK
Pricing Period................ December 8, 1997 through December 12, 1997
<TABLE>
<S> <C> <C>
Shares of Preferred Stock sold.......... 4,000 Average Market Price Shares
6,000 Additional Shares
10,000 Total Shares Sold
</TABLE>
Arithmetic Mean of the High and Low Sales
Prices of the Shares reported on the NYSE
(the "Average Market Price") for each
Trading Day of the Pricing Period:
<TABLE>
<CAPTION>
AVERAGE FOR
12/8/97 12/9/97 12/10/97 12/11/97 12/12/97 PRICING PERIOD
--------- --------- ---------- --------- --------- --------------
<S> <C> <C> <C> <C> <C>
$ 0.0000 $17.0000 $16.5938 $15.8750 $16.0313 $16.3750
</TABLE>
<TABLE>
<S> <C> <C>
High and Low Sales Prices at
which Average Market Shares
were sold during pricing
period...................... $17.1250 $16.0000
</TABLE>
Average Market Price Shares:
<TABLE>
<S> <C>
Gross Proceeds to Company....................................... $ 65,500.00
2% Discount..................................................... $ 1,310.00
-----------
Net Proceeds to Company......................................... $ 64,190.00
Gross Proceeds to Agent......................................... $ 65,312.50
Compensation to Agent........................................... $ 1,122.50
-----------
Net Proceeds to Company......................................... $ 64,190.00
Additional Shares Sold:
Gross Proceeds to Company........................................ $ 97,537.50
Commission to Agent.............................................. $ 1,950.75
-----------
Net Proceeds to Company.......................................... $ 95,586.75
Total Net Proceeds to Company ................................... $159,776.75
Total Compensation to Agent...................................... $ 3,073.25
</TABLE>
On December 12, 1997, the last reported sales price of the shares of Series B
Preferred Stock on the NYSE was $16.0000 per share.
Note: S.E.C. fees were not used in arriving at any of the above figures.
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL
OFFENSE.
THE ATTORNEY GENERAL OF THE STATE OF NEW YORK HAS NOT PASSED ON OR ENDORSED
THE MERITS OF THIS OFFERING. ANY REPRESENTATION TO THE CONTRARY IS UNLAWFUL.
----------------
THE DATE OF THIS PROSPECTUS SUPPLEMENT IS DECEMBER 16, 1997.
