Dr. Simmons is one of the original founding physicians of West Gastroenterology Medical Group. Dr. Simmons entered private practice in Los Angeles in 1980. He has been appointed to numerous positions including Chief of Medicine and Chief of Staff at Robert F. Kennedy Hospital. Since 1987, Dr. Simmons has conducted over 80 clinical trials for various pharmaceutical companies. He is a Clinical Instructor in Gastroenterology and a Clinical Assistant Professor of Medicine at the UCLA-Wadsworth VA Hospital Center. Dr. Simmons became a Diplomat of the American Board of Gastroenterology in 1981. Dr. Simmons is a member of the American Medical Association, National Medical Association, American College of Gastroenterology, American Gastroenterological Association, Golden State Medical Association, and Association of Clinical Research Professionals.