He was director of the Vietnam Head Injury Study and Founder, Principal Investigator, and first Director of the Defense and Veterans Head Injury Program, a national head injury disease management and clinical research effort. His research background includes neurodegenerative diseases, multiple sclerosis (MS), AIDS, neurooncology, and neurotraumatology. He is author on over 250 publications and presentations, and has conducted numerous clinical studies, including in head injury, AIDS, early and later pivotal clinical studies of beta-interferon (Avonex) in multiple sclerosis, and pilot studies of Hiltonol in brain tumors, MS, and AIDS.