Samuel James Dennis, 72, a retired economist with the Bureau of the Census and a former Falls Church city councilman, died of congestive heart failure Thursday at Commonwealth Doctors Hospital in Fairfax.

Mr. Dennis came to Washington in 1934 as an associate research economist with the Central Statistical Board.

In 1938, after a year of graduate study at Harvard University, where he earned a master's degree in economics, he returned here a chief of the construction and real property section in the Department of Commerce's old bureau of foreign and domestic commerce.

During World War II, Mr. Dennis served as director of analysis in the Office of the Defense Housing Coordinator. He also served with the National Housing Agency, as acting director of the NHA's housing market service and as chief of the agency's housing economics section.

After the war, Mr. Dennis returned to the Commerce Department as chief of the economics and statistics section in the office of domestic commerce.

From 1949 to 1954, he worked for the Economic Cooperation Adminstration, and its successor, the Mutual Security Agency, here and in Paris.

Mr. Dennis then transferred to the Bureau of the Census, where he was assigned as an advisor to the government of Pakistan and later directed bureau surveys on national health, population distribution and household food inventories. He was chief of the construction statistics division when he retired in 1971.

He then was an economic and statistics consultant for several years.

A resident of Reston, Mr. Dennis fomerly lived in Falls Church, where he served on the planning commission and played a major role in the incorporation of the City of Falls Church. He also was a Falls Church city councilman for nine years. He was a member of the Arlington Unitarian Church and the Reston Community Church.

Mr. Dennis also was active in Reston community affairs and was a chief architect of the proposed Town charter for Reston, which will be voted upon in November.

He was born in Bloomsburg, Pa. and earned a bachelor's degree in mathematics from Dartmouth College.

Survivors include his wife, Maurine P., of Reston; two sons, Robert, of Amissville, Va., and John of Arlington; a sister, Hope D. Anderson of Reston and three grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to Dartmouth College in Hanover, N.H., or to the Reston Community Church.