Filed Pursuant to Rule 424(b)(3) Registration File No.: 333-99693 PROSPECTUS SUPPLEMENT (TO PROSPECTUS DATED OCTOBER 31, 2002) L-3 COMMUNICATIONS HOLDINGS, INC. 448,582 Shares of Common Stock This prospectus supplement relates to 448,582 shares of Common Stock that may be sold by certain selling stockholders. This prospectus supplement, which supplements our prospectus dated October 31, 2002, contains information about the selling stockholders. NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS SUPPLEMENT IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE. July 8, 2004

TABLE OF CONTENTS PAGE ---- Selling Stockholders ...................................................... S-1 You should rely only on the information contained in this prospectus supplement and the prospectus to which it refers. We have not authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus supplement shall not constitute an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus supplement and the prospectus to which it refers is accurate only as of their respective dates. i

SELLING STOCKHOLDERS The selling stockholders listed below received shares as consideration in connection with our acquisition of ComCept, Inc. ("ComCept"). The following table states the number of shares of our outstanding common stock that the selling stockholders own resulting from payments made in our common stock in connection with our acquisition of ComCept, the number of such shares that may be sold for the account of the selling stockholders (or any of their donees with respect to donations to any such donee that does not exceed 500 shares), and the number of shares that will be owned by the selling stockholders assuming the sale of all the shares offered hereby. NUMBER OF NUMBER OF NUMBER OF SHARES OF SHARES OF SHARES OF COMMON STOCK COMMON STOCK COMMON STOCK SELLING STOCKHOLDER OWNED TO BE SOLD OWNED AFTER SALE - ------------------- ------------ ------------ ---------------- Robert L. Amick 13,147 13,147 0 Dennis R. Baas 13,147 13,147 0 George Bach 166 166 0 B&B Cullen Family LTD 95,504 95,504 0 Elizabeth Beasley 166 166 0 Claude Bennett 332 332 0 Tracy Benninger 874 874 0 Mark Bigham 12,082 12,082 0 Pressly Bonner 208 208 0 David Bryson 5,832 5,832 0 Thi Cao 40 40 0 Adelbert W. Carpenter 9,321 9,321 0 Christopher Christon 6,610 6,610 0 Neal B. Cooper 17,478 17,478 0 Max Corneau 332 332 0 Brian D. Cullen 50,102 50,102 0 Cullen Family Foundation 34,000 34,000 0 Gary Davis 4,882 4,882 0 Charles DeGilio 166 166 0 Paul Deuell 40 40 0 Robert E. Dryden 33,066 33,066 0 Robert S. Dunn 519 519 0 George M. Eargle 17,068 17,068 0 Chris Freeze 250 250 0 James C. Glenn, Jr. 1,907 1,907 0 Evan Goen 166 166 0 Joseph Goodman 2,916 2,916 0 Rose Goodrich 124 124 0 Michael C. Greer 26,837 26,837 0 Rebecca Hensley 208 208 0 Michell Hilton 82 82 0 James Higdon 82 82 0 Janey Hood 998 998 0 Ben K. Howell 3,706 3,706 0 Jamie Hydrick 208 208 0 Emily Juricek 166 166 0 John Langan 82 82 0 Edward Lavallee 208 208 0 Jim Mask 2,832 2,832 0 Greg Miller 1,208 1,208 0 Susan Mitchell 82 82 0 Bob Mimlitch 416 416 0 Art Money 1,666 1,666 0 Dick Murphy 166 166 0 Newbury Piret Companies, Inc. 10,954 10,954 0 John Parker 624 624 0 Kevin Powell 82 82 0 Art Sikes 708 708 0 Don Smith 416 416 0 Robert R. Spaulding 1,160 1,160 0 Lex E. Thorton 2,665 2,665 0 Bruce Trego 4,166 4,166 0 David Tschoerner 9,990 9,990 0 Jim Turner 2,498 2,498 0 Darrell Villarma 982 982 0 Maria Valdez 82 82 0 Greg Voelcker 82 82 0 Mark R. Von Schwartz 23,251 23,251 0 Frederick L. Wahl 9,688 9,688 0 Dee Ann Watkins 3,505 3,505 0 Anne Wester 2,082 2,082 0 John C. Wester and Anne L. Wester JT 5,025 5,025 0 TEN WROS Chris White 2,208 2,208 0 Mark Wilhelm 2,332 2,332 0 Curtis Wold 166 166 0 Philip A. Yates 4,758 4,758 0 Kathy Young 40 40 0 Phil Young 1,666 1,666 0 ------- ------- --- 448,522 448,522 0 ======= ======= === S-1