<PAGE>
THIS FILING LISTS SECURITIES HOLDINGS REPORTED
ON THE FORM 13F FILED ON FEBRUARY 14, 2000
PURSUANT TO A REQUEST FOR
CONFIDENTIAL TREATMENT AND FOR WHICH
THAT REQUEST
EXPIRED ON MAY 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: December 31, 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
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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 May 15, 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
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Form 13F Information Table Entry Total: 20
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Form 13F Information Table Value Total: $344,576
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(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/ UT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN ALL DISCRETION MANAGERS SOLE SHARED NONE
-------------- -------------- ----- -------- ------- --- --- ---------- -------- ---- ------ ----
<S> <C> <C> <C> <C> <C> <C> <C> <C> <C> <C> <C>
Aerial
Communications Common 007655103 4,042 66,400 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
Aironet Wireless Common 00943A107 2,671 40,000 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
Alza Corp. Common 026615108 44,227 1,277,300 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
Aviall, Inc. Common 05366B102 2,223 271,500 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
CBS, Inc. Common 12490K107 8,683 135,800 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
Clarify, Inc. Common 180492100 38,250 301,700 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
CMP Group, Inc. Common 125887109 10,198 370,000 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
DII Group, Inc. Common 232949107 7,452 105,000 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
Eastern Utilities Common 277173100 3,513 115,900 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
Esat Telecom Common 26883Y102 7,073 77,300 SH SOLE SOLE
- ----------------------------------------------------------------------------------------------------------------------------------
</TABLE>
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/ UT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN ALL DISCRETION MANAGERS SOLE SHARED NONE
-------------- -------------- ----- -------- ------- --- --- ---------- -------- ---- ------ ----
<S> <C> <C> <C> <C> <C> <C> <C> <C> <C> <C> <C>
Jones Intercable Common 480206200 6,183 89,200 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
Maker
Communications Common 560875106 214 5,000 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
Michael Foods Common 594079105 1,539 62,500 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
MidAmerican Energy Common 595920109 15,210 451,500 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
New England Electric Common 644001109 14,443 279,100 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
Omnipoint Corp. Common 68212D102 106,222 880,600 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
Players International Common 727903106 700 85,200 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
Reynolds Metals Common 761763101 63,568 829,600 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
Waste Management Common 94106L109 5,859 340,900 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
Wicor, Inc. Common 929253102 2,306 79,000 SH SOLE SOLE
- -------------------------------------------------------------------------------------------------------------------------------
</TABLE>
