Arthur S. Elstein, Ph.D. has said that he has been motivated to address two research questions throughout this career: How do physicians make decisions? and How can we help them make better ones? He has addressed these questions using the tools of a psychologist but the results of his research in medical cognition, medical reasoning, and judgement have had a lasting impact on medical education and how future physicians are prepared. Further, through teaching and mentoring, he has produced a second generation of medical education researchers and leaders; and perhaps most importantly, through his role modeling of skepticism and scholarship, he has taught what a professional educator must do to succeed in medical education. His distinguished thirty-eight year career was primarily at the Office of Medical Education Research and Development at Michigan State University's College of Human Medicine (1968-1994) and, after his retirement there, in the Department of Medical Education and the School of Public Health at the University of Illinois at Chicago. During his career he authored or edited four books, wrote 22 book chapters, published 99 articles, and made more than 900 presentations. He received many prestigious awards. This article gives an overview of Elstein's career and accomplishments and his perspectives on significant innovations in medical education, the role of professional medical educators, the major lessons he has learned during his career.