Gary N. Horlick has been named a partner in the Washington law firm of O'Melveny & Myers. Horlick is currently a deputy assistant secretary for import administration of the Department of Commerce.

Julian W. Fore has joined the economics consulting firm of Gladstone Associates. Fore was formerly acting director and chief economist of the city of Cleveland's department of economic development.

Warren S. Rosenfeld has been named a partner in the Wasington law firm Malley, Yelsky, Chernove & Scott. Brad D. Weiss and Mitchell B. Rosenfeld have been named associates of the firm.

John J. Renner II, Paul H. Kositzka and Michael E. Wicks have established a certified public accounting firm in Alexandria. They were formerly associates of the firm of Minter, Morrison and Grant, also in Alexandria.

Paul Fabricant has been promoted to vice president for taxes of Dynalectron Corp. Philip B. DuPriest has been named director of marketing for government services of Dynalectron's technical services group. DuPriest was formerly senior marketing representative in Washington for the Boeing Corp.

Lillian Greitzer has established Business Options, an Alexandria marketing and management firm. Greitzer also heads Temporary Options Inc. and Creative Options Inc. L.Z. Buddy Peoples has been named director of Business Options' printing brokerage services division.

George C. Thomasson has established Thomasson Architects in Washington. He was formerly vice president and director of the Washington office of TAG Architects.

Lawrence F. Tashbook has been named vice president for marketing of U.S. Design Corp. Tashbrook was formerly with Digital Equipment Corp.

Robert R. Humphreys and Joseph A. Mitchell have established the Washington law firm of Humphreys & Mitchell. Humphreys was formerly commissioner of the Department of Education rehabilitation services administration. Mitchell was formerly director of the Agency for International Development foreign disaster assistance administration.

Walter Wilowatyj has been named senior vice president and chief financial officer of Psych Systems Inc., a Baltimore developer of computerized testing systems.

C. Edward Brickley has been named vice president and general manager of United Health Maintenance in Columbia. He was formerly controller.

Barry Koh has been named president of Hittman Nuclear & Development Corp., a subsidiary of Westinghouse Electric Corp. In a related matter, Ralph DiSibio, Hittman's director of disposal site operations, has been named to the Maryland Medical and Industrial Radiation Users Group.

John T. Ketterer has been named director of marketing of MDI Securities Corp. in Glen Burnie. He was formerly a vice president of Mace Advertising Agency.

John L. Green has been named vice president for planning and marketing of the Washington Hospital Center Health System. He is currently deputy secretary of the Maryland department of health and mental hygiene.

Carl S. Silverberg has joined Shearson/American Express as a tax-shelter consultant. He was formerly vice president of Winthrop Securities Corp.