 Rahbar spent 1968–1969 as a visiting scientist at the Department of Medicine of the Albert Einstein College of Medicine in New York, where he collaborated with Helen M. Ranney.After his return to Tehran, Rahbar was promoted to full professor in 1970 and to director of the Department of Applied Biology in the University of Tehran Medical School in Tehran.1979 Rahbar became a researcher and professor of diabetes in the Department of Diabetes, Endocrinology, and Metabolism at the City of Hope in Duarte, California (in Los Angeles County).