 He became a postdoctoral clinical and research fellow in medicine at the Massachusetts General Hospital and a postdoctoral research fellow in medicine at Harvard Medical School in 1991.Pestell was recruited as an assistant professor in the Department of Molecular Medicine at Northwestern University's Feinberg School of Medicine in Chicago, Illinois.He became an associate professor, and professor, in the Departments of Medicine and Developmental and Molecular Biology at the Albert Einstein College of Medicine in New York, New York.