Retired Navy Cmdr. Ronald R. Mason, 42, a 20-year Navy veteran who had served as a line officer in the Mediterranean and as a staff officer in Vietnam, died of cancer Friday at the Bethesda Naval Hospital.

Cmdr. Mason was assigned to this area in 1974. He was a budget analyst with the Navy's management resources directorate and served in the Navy's Material Command before retiring from active duty in August 1980.

He served in Saigon from 1965 to 1966. He saw extensive duty aboard destroyers and destroyer escorts in the Mediterranean. He also had been executive officer of an ammunition ship there.

Cmdr. Mason was a native of Canandaigue, N.Y. He received his officer's commission in 1960 after graduating from Miami University in Oxford, Ohio. He received a master's degree in personnel management from George Washington University in 1977.

He had lived in Annandale since 1974 and was a member of the Holy Spirit Catholic Church there. He also had been active in the Little League, where he had been a coach and deputy commissioner.

Survivors include his wife, Kathleen M., two sons, Richard Charles and Patrick Thomas, and a daughter, Susan Katherine, all of Annandale, and a sister, Stephany A. McIntyre, and his maternal grandmother, Elizabeth Dubler, both of Canandaigua.