In 1996 the 75th anniversary of the discovery of insulin was celebrated at the University of Toronto, the scene of that discovery in 1921. This volume was stimulated by the scientific program which was staged at that time and brought together much of the world''s best talent to discuss and analyze the most recent developments in our understanding of pancreatic function, insulin secretion, the interaction of insulin with its target tissues, the mechanism of insulin action at the cellular level, and the defects which underlie both Type I (insulin-dependent diabetes mellitus, IDDM) and Type II (noninsulin-dependent diabetes mellitus, NIDDM) forms of the disease. We have chosen to focus the present volume on work related to insulin action.