This paper surveys Herbert A. Simon's work over more than five decades of research, focusing particularly on his early publications and his contributions to behavioral economics, including the importance of the interdisciplinary research program with which he was associated at Carnegie Mellon University in the1950s and early 1960s. We argue that although his influence extended over political science, psychology, economics, sociology, philosophy, administrative theory, public administration, and computer science, there is a considerable continuity in Simon's writings. In particular, he persistently sought to clarify the real processes of human decision making, thus was pre-eminently a behavioral economist.