S. R. (Si) Smith, 70, a retired Agriculture Department official, died of cancer Aug. 2 in Columbus, Mont., where he made his home.

He retired in 1967 after serving for two years as administrator of the department's Consumer and Marketing Service. Before that, Mr. Smith had been administrator for four years of the Agricultural Marketing Service.

Born in Dolton, S.D., he received a degree in economics from the University of Montana and took graduate studies at the University of California.

Mr. Smith joined the Agriculture Department in 1934 as an economic analyst with the Agricultural Adjustment Administration.

He seraed in various positions in the department's fruit and vegetable marketing services. During World War 11, he was with the War Food Administration and was director of its office of distribution in 1943-44.

From 1946 to 1953, Mr. Smith was director of the fruit and vegetable branch of the production and marketing administration. He then served for eight years as director of the fruit and vegetable division of the Agriculture Marketing Service before becoming its administrator in 1961.

Mr. Smith held the Agriculture Department's Distinguished Service Award.

His survivors include a daughter, Gerry Lynn Gilboe, and one grandchild.