<PAGE>
THIS FILING LISTS SECURITIES HOLDINGS REPORTED
ON THE FORM 13F FILED ON NOVEMBER 15, 1999
PURSUANT TO A REQUEST FOR
CONFIDENTIAL TREATMENT AND FOR WHICH
CONFIDENTIAL TREATMENT
EXPIRED ON FEBRUARY 15, 2000
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
Form 13F
FORM 13F COVER PAGE
Report for the Calendar Year or Quarter Ended: September 30, 1999
Check here if Amendment /X/; Amendment Number: 1
This Amendment (Check only one.): // is a restatement.
/X/ adds new holdings entries.
Institutional Investment Manager Filing this Report:
Name: Chesapeake Partners Management Co., Inc.
Address: 1829 Reisterstown Road
Suite 220
Baltimore, Maryland 21208
Form 13F File Number: 28-4120
The institutional investment manager filing this report and the person by whom
it is signed hereby represent that the person signing the report is authorized
to submit it, that all information contained herein is true, correct and
complete, and that it is understood that all required items, statements,
schedules, lists, and tables, are considered integral parts of this form.
Person Signing this Report on Behalf of Reporting Manager:
Name: Mark D. Lerner
Title: Vice President
Phone: (410) 602-0195
Signature, Place, and Date of Signing:
/s/ Mark D. Lerner Baltimore, Maryland February 14, 2000
--------------------------- ------------------- ----------------------
[Signature] [City, State] [Date]
Report Type (Check only one.):
/X/ 13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager
are reported in this report.)
// 13F NOTICE. (Check here if no holdings reported are in this report, and
all holdings are reported by other reporting manager(s).)
// 13F COMBINATION REPORT. (Check here if a portion of the holdings for this
reporting manager are reported in this report and a portion are reported
by other reporting manager(s).)
<PAGE>
FORM 13F SUMMARY PAGE
Report Summary:
Number of Other Included Managers: 0
--------
Form 13F Information Table Entry Total: 26
--------
Form 13F Information Table Value Total: $285,356
--------
(thousands)
List of Other Included Managers:
Provide a numbered list of name(s) and Form 13F file number(s) of all
institutional investment managers with respect to which this report is filed,
other than the manager filing this report.
[If there are no entries in this list, state "NONE" and omit the column headings
and list entries.]
None
<PAGE>
FORM 13F INFORMATION TABLE
<TABLE>
<CAPTION>
COLUMN 1 COLUMN 2 COLUMN 3 COLUMN 4 COLUMN 5 COLUMN 6 COLUMN 7 COLUMN 8
- --------------------- ---------------- -------- -------- ------------------------- ---------- -------- ----------------
VALUE SHRS OR SH/ PUT/ INVESTMENT OTHER VOTING
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN CALL DISCRETION MANAGERS AUTHORITY
- --------------------- ---------------- -------- -------- ---------- ---- ----- ---------- -------- ----------------
SOLE SHARED NONE
---- ----- ----
<S> <C> <C> <C> <C> <C> <C> <C> <C> <C> <C> <C>
Abacus Direct Common 002553105 $33,869 277,900 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Acquarion Company Common 03838W101 $624 17,400 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
AFC Cable Systems Common 000950105 $4,335 102,000 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Big Flower Holdings Common 089159107 $8,499 300,200 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Caremark Common 58503X107 $35,394 6,155,500 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Conoco Class B Common 208251405 $7,757 283,347 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Filenes Basement Common 316866102 $143 316,500 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Healthsouth Common 421924101 $1,746 285,000 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Mattel, Inc. Common 577081102 $15,215 800,780 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Navigant Consulting Common 63935N107 $5,797 125,000 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Nichols Research Common 653818104 $908 34,100 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Outdoor Systems Common 690057104 $38,435 1,075,100 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Pacificorp Common 695114108 $2,214 110,000 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Perclose, Inc. Common 71361C107 $20,790 446,500 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Premark Common 740459102 $25,518 505,300 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Republic New York Common 760719104 $49,500 805,700 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Republic New York Common 760719104 $5,671 92,300 SH CALL SOLE N/A
- -----------------------------------------------------------------------------------------------------------------------------------
Rite Aid Common 767754104 $4,392 318,000 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Rite Aid Common 767754104 $1,727 125,000 SH CALL SOLE N/A
- -----------------------------------------------------------------------------------------------------------------------------------
Roberts Pharm. Common 770491108 $3,234 106,900 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Smart Modular Tech Common 831690102 $3,798 111,500 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Stanford Telecom Common 854402104 $907 28,500 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Transaction Network Common 893414102 $1,963 50,000 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
United Globalcom Common 910734102 $2,938 40,800 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
US Bioscience Common 911646206 $1,810 127,000 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
Wyman Gordon Common 983085101 $8,172 437,300 SH SOLE SOLE
- -----------------------------------------------------------------------------------------------------------------------------------
</TABLE>
