Rush V. Greenslade, 61, an employe of the Central Intelligence Agency for more than 20 years when he retired in 1973, died of cancer Friday at Suburban Hospital.

Mr. Greenslade came to Washington and joined the CIA in 1951. He was a supervisor of economic research concerning the Soviet Union and eastern Europe from 1954 until he retired in 1973.

He taught economics and statistics as a part-time instructor at American University from 1963 to 1970 and at Johns Hopkins University's School of Advanced International studies from 1973 to 1977. He also had taught at Howard University and the University of Virginia.

After his retirement from the CIA, Mr. Greenslade became an economic reserach consultant in Washington.

He was born in Tulsa, Okla. He earned a backelor's degree at Princeton University and a doctorate at the University of Chicago.

He received the Silver Star for his service in the Pacific during World War II with the Army Air Corps.

Mr. Greenslade was awarded the Distinguished Intelligence Service Medal in 1973.

He is survived by his wife, Gertrude, of the home in McLean; three sons, Richard, of Colorado Springs, Colo., and Rush V. Jr. and Robert, both of Spokane, Wash., and a sister, Sara Jane LaSelle, of Santa Fe, N.M.

The family suggests that expressions of sympathy may be in the form of contributions to the scholarship fund at St. Albans School for Boys.