Insider Transactions is a weekly report of stock transactions involving officers and directors of publicly owned local companies.

Stock trading by corporate insiders often is a bellwether of corporate health.

Most insiders buy stock or exercise options to make a profit.

And insiders may be selling stock for tax reasons, estate planning or cash needs.

The following insider transactions involving companies in the Washington, Baltimore and Richmond areas were compiled by States News Service from reports to the Securities and Exchange Commission. AMERICAN MANAGEMENTSYSTEMS INC.

Patrick W. Gross, an officer of Arlington-based American Management Systems Inc., gave a 1,620-common-share gift Dec. 24, and exercised options to purchase 10,204 common shares for an unreported price Dec. 26. Gross owns 148,050 shares directly and 51,000 shares indirectly. BALTIMORE BANCORP.

Director Robert F. Comstock of Baltimore Bancorp. of Baltimore, purchased 7,500 common shares Dec. 6 through 26 at $4.13 to $5.38 each. Comstock presently holds 33,000 shares directly.BOWL AMERICA INC.

Director Abraham J. Levy of Alexandria-based Bowl America Inc. purchased 2,050 class A common shares at $16.50 to $17 each Dec. 4 to Dec. 5. He owns 2,697 class A shares directly and 43,506 class A shares indirectly.CHEMDESIGN CORP.

Richard P. Thomley, a director of Bethesda-based Chemdesign Corp., exercised options to purchase 3,038 common shares Dec. 11 at $1.71 to $3 each. He presently owns 18,331 shares directly.

Mark Rossi, a director, sold 10,000 common shares at $7.25 each Dec. 7, and currently owns 643,844 shares indirectly. COMPUTER DATA SYSTEMS INC.

Director Elmer B. Staats of Rockville-based Computer Data Systems Inc. sold 3,000 common shares at $8 each Dec. 4, dropping his direct holdings to 4,000 shares. ESSEX CORP.

Samuel Hopkins, a director of Essex Corp. of Alexandria, purchased 8,500 common shares Dec. 7 at $1.30 to $1.35 each, bringing his direct holdings to 11,000 shares.

Robert W. Hicks, a director, purchased 7,500 common shares at $1.30 to $1.35 each Dec. 7 through Dec. 10, bringing his direct holdings to 14,500 shares directly.ETHYL CORP.

William M. Gottwald, a vice president of Ethyl Corp. of Richmond, gave a 11,640 common-share gift Nov. 1. Gottwald controls 262,656 shares directly and 133,556 shares indirectly.FIDELITY BANCSHARES INC.

C. Eugene Whittle, a vice president of Fidelity Bancshares Inc. of Norfolk, purchased 2,274 common shares at $15.63 each Dec. 14. Whittle owns 3,850 shares directly. F&M NATIONAL CORP.

John S. Scully III, a director of F&M National Corp. of Winchester, Va., bought 2,000 common shares Dec. 26 at $9.50 each, to bring his direct holdings to 59,021 shares.GREATER WASHINGTON INVESTORS INC.

Johnston Industries Inc., a beneficial owner of Greater Washington Investors Inc. of Chevy Chase, purchased 63,700 common shares at $2.88 each Dec. 3 through Dec. 14, and now controls 1,535,906 shares directly and 1,164,237 shares indirectly.JAMES MADISON LTD.

James A. Baker, president of Washington-based James Madison Ltd., sold 2,000 class A common shares at $2 each Dec. 21, and now holds 2,000 class A shares indirectly.JAMES RIVER CORP.

Brenton S. Halsey, chairman of James River Corp. of Richmond, gave a 5,113 common-share gift Dec. 7, and exercised options to purchase 13,183 common shares Dec. 7 through Dec. 27 at $6.85 each. Halsey controls 603,373 shares directly and 58,476 shares indirectly.MID-ATLANTIC MEDICAL SERVICES INC. John L. Ford, a director of Mid Atlantic Medical Services Inc. of Rockville, sold 5,620 common shares at $8.75 each Dec. 19. He holds 304,284 shares directly and 65,100 shares indirectly.TEMPEST TECHNOLOGIES INC.

Delaney E. Blaine, chairman of Herdon-based Tempest Technologies Inc., privately purchased 7,559 common shares at 38 cents each Dec. 16, bringing his direct holdings to 357,033 shares.THE WASHINGTON POST CO.

Joel Chaseman, a vice president of The Washington Post Co., sold 5,000 class B common shares at $200 each Dec. 18. He now holds 8,614 class B shares. USLICO CORP.

Eli Weinberg, a director of Arlington-based USLICO Corp., purchased 1,000 common shares at $15 each Nov. 15, and now holds 4,500 shares directly.