A native of New York, Dr. Fenster graduated cum laude from Brandeis University in 1970. He received his medical training at the State University of New York, Health Sciences Center at Brooklyn. After completing his internship in Internal Medicine at Brooklyn in 1975, he moved to Tucson. Following his residency in Internal Medicine at The University of Arizona College of Medicine, he completed a Cardiology Clinical Fellowship and Research Fellowship at The University of Arizona. He was a recipient of an American Heart Association Clinician-Scientist Award from 1980 to 1985 for the study of pharmacokinetic and dynamic effects of cardiac drugs.