Donald Vance Cox, 63, a retired Navy rear admiral who commanded the cruisers and destroyers of the 7th Fleet off Vietnam in 1970, died Dec. 5 at his home in Fairfax. He had leukemia and amyotrophic lateral sclerosis, also known as Lou Gehrig's disease.

Adm. Cox was born in Farragut, Iowa. He graduated from the U.S. Naval Academy at Annapolis and earned a master's degree in ordnance engineering at Johns Hopkins University. He moved to Washington in 1953.

During World War II, he served in the Pacific on the battleship Idaho and on the destroyer Maddox. His postwar assignments included command of the Robinson, a destroyer, and the Chicago, a cruiser.

In 1969, he took command of the training command of the Pacific Fleet. The following year he took over Cruiser-Destroyer Group III and then was made commander of all cruisers and destroyers in the 7th Fleet. He later served as assistant deputy chief of naval operations for surface warfare. He was deputy chief of staff for operations for the Atlantic Fleet when he retired in 1974.

He later was a consultant with the Kaman Aerospace and Sciences corporations and the Ketron Corp., all in Arlington.

In private life, Adm. Cox enjoyed painting and his work was exhibited at the Washington Navy Yard.

Survivors include his wife, the former Evelyn Brewer, and a daughter, Gena C. Duncan, both of Fairfax; two sons, Donald V. Jr., of Richmond, and Navy Lt. Thomas E., of Virginia Beach; his mother, Mrs. Ralph E. Cox of Farragut, and three grandchildren.