Montis R. Klepper, 63, a former assistant director of the U.S. Geological Survey, died of cancer Sunday at his home in Reston.

Dr. Klepper joined the survey in 1941. His first assignment included surveys for tungsten in Nevada and elsewhere in the West under the World War II strategic minerals program. He also worked in Brazil, Japan, Korea and Indonesia. But most of his field work was done in western Montana, where he explored for minerals and did research on the Boulder batholith.

He was transferred to Washington in 1957 and has been a resident of this area since. He served as assistant and then associate chief geologist of the survey. He was assistant director from 1972 until 1977, when he resigned to resume his field studies in Montana.

In 1978, Dr. Klepper received the Distinguished Service Award from the Department of the Interior, of which the Geological Survey is a part.

He was a member of the Geological Society of America, the Society of Economic Geologists, the American Institute of Mining Engineers, and the American Association for the Adcancement of Science. He was president of the Geological Society of Washington in 1969.

Dr. Klepper was born in Lock Haven, Pa. and graduated from Pennsylvania State College in 1937. He earned a doctorate in geology from Yale University in 1948.

Survivors include his wife, Fern Carter Klepper, of the home; a son, Stewart, a law student at Boston University, and a brother, Judson, of Springfield, Pa.

The family suggests that expressions of sympathy be in the form of contributions to the Hospice of Northern Virginia, P.O. Box 1590, Arlington, Va. 22210.