John C. Shilloc, Jr., 73, a State Department Foreign Service officer for 34 years before his retirement in 1962, died Wednesday at Georgetown University Hospital after a stroke.

Early in his career, Mr. Shillock served at diplomatic posts in Argentina, Bolivia, Chile and Portugal.

During World War II, he was assigned to Morocco, Peru and Canada and later served as charge d'affaires in Paraguay. From 1954 to 1956, he was attached to the United Nations delegation in Geneva, Switzerland. He also was posted twice to the State Department here. His last assignment was as deputy chief of mission and charge d'affaires in Panama.

Mr. Shillock was born in Portland, Ore., and graduated from Reed College there.

Following his retirement, he made his home in Washington. He was a member of DACOR, an organization of retired diplomatic and consular officers.

Survivors, include his wife of 41 years, the former Mary Louise Hess of Washington; a son, John III of Minneapolis; a sister, Elizabeth Bechtold, and two brothers, Max M. and Frank T., all of Portland and two grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the DACOR Educational and Welfare Foundation in Washington.