Eugene C. Rich, M.D., is a senior fellow at Mathematica Policy Research. Dr. Rich is an expert on sources of practice variation in medical care with a focus on the influence of the policy, payment, and practice environments on health professionals’ decision making. As a practicing general internist, he also has a long-standing interest in improving the delivery of primary care and the policies needed to accomplish this. He is a senior editor of the Journal of Comparative Effectiveness Research. Dr. Rich holds an M.D. from Washington University School of Medicine in St. Louis.