Polyuria, polydipsia, polyphagia, and mellituria have been recognized since antiquity as the classic symptoms of diabetes mellitus. Research has shown, however, that diabetes is not a single disease but a group of disorders having in common hyperglycemia. In addition to its effects on carbohy drate metabolism, diabetes also affects the metabolism of protein and fat and commonly leads to serious complications affecting many organ systems. In its various forms, diabetes afflicts about 5% of the population in most Western societies (1).

Studies of the natural history and pathogenesis of hyperglycemia, together with recent advances in biotechnology, have led to the system of classification developed by the National Diabetes Data Group (2). Among the various diabetic syndromes now recognized, insulin-dependent dia betes mellitus (IDDM or Type 1 diabetes) and noninsulin-dependent diabetes mellitus (NIDDM or Type 2 diabetes) account for the great majority (> 90%) of patients with the disease. The principal features that distinguish IDDM and NIDDM are summarized in Table 1. In this review we shall focus on advances in the study of IDDM, a syndrome believed to have an autoimmune pathogenesis.