Since the publication of the first edition of The Diabetic Pancreas in 1977, much progress has been made in various areas of diabetes research. While only a rela- tively short while ago diabetes was considered a single disease, in more recent years it has become apparent that it is a heterogeneous group of disorders, all of which are characterized by a decreased tolerance of carbohydrates and most of which have a genetic basis, although the genetic types vary. In more recent years, an International Work Group sponsored by the National Diabetes Data Group of the NIH proposed a w generally accepted classification, according to which the insulin-dependent ketosis-prone diabetes, formerly and inappropriately called the juvenile type, is considered a subclass of diabetes, type 1. Because it can occur at any age, it was recommended that the diagsis based on age be eliminated. The n-insulin-dependent, n-keto sis-prone type of diabetes, which is t secondary to other diseases or conditions, and which was formerly called matu- rity-onset diabetes, was considered a second subclass, type II, because although this form usually develops after age 40, it also occurs in young persons, who do t require insulin or are t ketotic. Although this classification is t entirely agreed upon by all diabetologists, for practical purposes it has been generally accepted and has been utilized by the contributors to this volume.