<PAGE>
Prospectus Supplement filed under Rule 424(b)(3)
in connection with Registration Statement No. 333-48047
PROSPECTUS SUPPLEMENT NO. 2 DATED AUGUST 31, 1998
(To Prospectus Dated May 28, 1998 as supplemented by Prospectus Supplement No. 1
Dated July 13, 1998)
PLATINUM technology, inc.
$150,000,000 6.25% Convertible Subordinated Notes Due 2002
and Shares of Common Stock Issuable Upon Conversion Thereof
This Prospectus Supplement No. 2 (the "Second Prospectus Supplement")
supplements information contained in that certain Prospectus, dated May 28,
1998 (the "Prospectus") as supplemented by that certain Prospectus Supplement
No. 1, dated July 13, 1998 (the "First Prospectus Supplement"), relating to the
offer and sale by certain Selling Securityholders of up to $150,000,000 6.25%
Convertible Subordinated Notes Due 2002 and shares of Common Stock issuable upon
conversion thereof (the "Securities") of PLATINUM technology, inc. (the
"Company"). This Second Prospectus Supplement is not complete without, and may
not be delivered or utilized except in connection with, the Prospectus and
First Prospectus Supplement, including any amendments or supplements thereto.
Capitalized terms used herein but not defined have the meanings assigned to such
terms in the Prospectus. The following table amends and supplements the
information set forth in the Prospectus and the First Prospectus Supplement
under the caption "Selling Securityholders."
<TABLE>
<CAPTION>
Principal Amount of
Securities Beneficially Owned
--------------------------------------------
Number of
Number of Principal Shares of
Principal Shares of Amount of Common Stock
Amount of Common Notes That That May
Name Notes Percentage Stock (1)(2) May Be Sold Be Sold
- ------------------------------------ ----------- ---------- ------------ ----------- ------------
<S> <C> <C> <C> <C> <C>
First Delta Securities $ 200,000 * 5,547 $ 200,000 5,547
JP Morgan Securities Incorporated 1,500,000 1.0 41,605 1,500,000 41,605
Any other holders of Notes (3)(4) 27,725,000 18.5 769,017 27,725,000 769,017
</TABLE>
- --------------------
* Less than 1%.
(1) Assumes conversion of the full amount of Notes held by such holder at the
initial rate of $36.0525 in principal amount of Notes per share of Common
Stock; such conversion price is subject to adjustment as described in the
Prospectus under "Description of Notes - Conversion." Under the terms of
the Indenture, fractional shares will not be issued upon conversion of the
Notes; cash will be paid in lieu of any fractional shares.
(2) The number of conversion shares beneficially owned by each Selling
Securityholder named herein is less than 1% of the company's outstanding
Common Stock as of August 31, 1998.
(3) Information concerning other Selling Securityholders will be set forth in
supplements to this Prospectus from time to time, if required.
(4) Assumes that "Any other holders of Notes" do not beneficially own any
Common Stock other than the Common Stock issuable upon conversion of the
Notes at the initial conversion price.
This Prospectus Supplement is dated August 31, 1998
