Harry L. Merrick Sr., 79, a Washington advertising executive and a former president of the Metropolitan Washington Board of Trade and the Kiwanis Club of Washington, died Nov. 12 at his home in Potomac. He had myasthenia gravis, a disease of the nervous system.

Mr. Merrick was chairman of the executive committee of Kal, Merrick & Salan Inc. of Bethesda, an advertising firm with which he had been associated since 1925. He became a partner of the company in 1935 and had served as its president from 1956 to the early 1970s.

In 1958, he received the Award of Achievement of the Washington Advertising Club.

Mr. Merrick was a trustee of the Federal City Council; a director of the Boys Club of Washington, the Metropolitan Police Boys Club, Capitol Hill Hospital and the D.C. chapter of the American Red Cross, and a member of the executive committee of the National Capital Area Council of Boy Scouts of America. He was a member of the Congressional Country Club.

He also was a director of or adviser to several businesses in the area.

Mr. Merrick was born in Portsmouth, Ohio. He grew up in Washington and graduated from Rockville High School. He attended the National School of Fine and Applied Art.

He began his advertising career in 1923. In 1925, he joined what was then the Kal-Williams Advertising Agency as a copy, layout and account executive.

His marriage to Irma Merrick ended in divorce.

Survivors include his wife, Mary M., of Potomac; a son by his first marriage, Harry L. Jr., of Chevy Chase; three children by his second marriage, David C., of Potomac, Mary L., of Washington, and William E., of Rockville; a sister, Suzanne Mullett Smith of Washington, and two grandchildren.