Kennedy Bank and Trust Co. of Bethesda has elected Lawrence I. Melton chairman of the board and president of the three-year-old bank. Melton has been president and a director for the past two years.

In addition, Kennedy B&T elected Anne F. Douglass a director. Douglass is vice president, treasurer and cashier of the bank. James C. Martin, currently a director, was named a vice president.

New Kennedy directors are Joseph P. Burke, director of civilian personnel at the National Security Agency and J. Frank Shoaf, executive vice president of the L. G. Balfour Co.

Martin Marietta Corp. of Bethesda elected Mary Jane LaBarge corporate secretary of the company and its wholy-owned subsidiary, Martin Marietta Aluminum, Inc. LaBarge, assistant secretary of both companies since 1974, was also elected a director of the parent company.

The Chessie System has named John W. Snow to a new position of vice president for government affairs here. Snow is a former highway safety administrator and deputy under secretary of transportation. Chessie is a rail holding company.

Robert R. Denny has resigned as executive vice president and director of Henry J. Kaufman & Associates to open his own marketing communications firm, Robert Denny & Associates.

Former chairman of the Council of Economic Advisors Alan Greenspan has been elected to the board of Shearson Hayden Stone, Inc., and will be an economic consultant to the investment banking firm.

At Shearson he joins former Federal Energy Administrator Frank Zarb, who returned to the firm he left when he came to Washington.

Greenspan has also been elected a director of Dreyfus Liquid Assets, Inc., and Dreyfus Special Income Fund. Inc.

Former Secretary of Commerce and Special Representative for Trade Negotiations Frederick B. Dent has been elected to the board of Armed Steel Corp.

Former Special Assistant to the President for Consumer Affairs Virginia H. Knauer has been elected to the board of Fideleor, Inc., parent company of Fidelity Bank in Philadelphia.

The Society of American Business and Economic Writers, which met in New York last week, elected Larry Birger president. Birger, business editor of the Miami News, succeeds Myron Kandel, business editor of the New York Post. Thomas Diamond, business editor of the Washington Star, was elected secretary.

At the first meeting of the University of the District of Columbia/Industry Cluster Program, Barbara Gruner of The Washington Post was elected industry co-chairman. She will serve with academic co-chairman R. Charles Long.