Type 1 diabetes mellitus (DM) is a chronic disorder of glucose homeostasis, and its clinical management is firmly in the domain of the diabetologist and endocrinologist. However, the disease arises as a result of immune destruction of the insulin-producing b cells in the pancreas, and therefore research into its pathogenesis is firmly rooted in the immunology laboratory. Worryingly, the incidence of Type 1 DM is on the increase in the developed world, especially in the under 5-year age group. This article presents an update of current understanding of the pathological events leading to clinical diabetes. It focuses on how this information is being used to promote cures, such as islet transplantation, and how it may be used in the future for the development of population screening and disease prevention strategies.