Retired Vice Adm. Laurence Hugh Frost, 74, former head of the National Security Agency and the Potomac River Naval Command, died Monday at Portsmouth (Va.) Naval Hospital.

He was commandant of the Potomac River Naval Command, from 1962 until his retirement in 1964. He moved to Norfolk in 1968.

Adm. Frost helped set up Vinson Hall in McLean, which was built by the Navy-Marine-Coast Guard Residence Foundation to house retured officers of those military branches, their wives, widows and mothers.

Adam. Frost first came to public attention several months before the attack on Pearl Harbor in December, 1941. As a lieutenant commander, he was skipper of the destroyer U.S.S. Greer, which was carrying mail to Iceland when it was attacked on Sept. 4 by a German submarine.

He maneurvered the Greer to avoid the torpedoes, made a counterattack and reported the incident. A week later, although this country was not yet at war, President Roosevelt announced in a worldwide radio address that the Navy was to attack any vessel threatening U.S. shipping.

Adam. Frost remained in command of the Greer until 1942, when he took command of the newly commissioned destroyed U.S.S. Waller and led it into combat in the Pacific.

The Walter participated in action in the southern Solomons and in the New Georgia operations. Adm. Frost received the Silver Star, a Gold Star in lieu of a second Silver Star and the Bronze Star.

Later in the war, he served as communications officer for the Commander Central Pacific Task Force and earned the Legion of Merit.

Adam. Frost returned to Washington in 1945 to serve in the division of naval communications in the Office of the Chief of Naval Operations. He then was transferred to Naval Intelligence until taking command of a destroyer squadron in 1948.

After graduating from the Naval War College, he took command in 1951 of the cruiser U.S.S. Manchester. She was sent to Korean waters during the conflict there to support the Marines with shore bombardment Adm. Frost was awarded another Gold Star in lieu of a second Legion of Merit.

In 1953, he was ordered to the National Security Agency Directorate, serving as chief of staff, and in 1956 returned here as assistant chief of naval operations (intelligence) and director of naval intelligence.

Adam. Frost assumed duty as director of the National Security Agency at Ft. Meade in 1960, until taking over the Potomac River Naval Command two years later.

Born in Fayetteville, Ark, he attended the University of Arknasas for a year before his appointment to the Naval Academy at Annapolis, where he graduated in 1926.

He saw duty as a line officer aboard battleships and destroyers and attended the Postgraduate School at Annapolis from 1933 to 1935.

He is survived by his wife, Louise Albers Forst, of the home in Norfolk; a son, Laurence W., also of Norfolk; a sister, Sue F.English, of Los Angeles, and four grandchildren.