In spite of the potential assay problems, a relatively clear general picture concerning islet cell antibodies has emerged. They are undoubtedly the most potent indicator of risk for insulin-dependent diabetes, at least among high-risk persons (that is, first-degree relatives of insulin-dependent diabetics). Islet cell antibodies have been the focus of intense research scrutiny over the last decade, yet their etiologic role remains unclear. In patients with insulin-dependent diabetes, there is no striking relation at onset between islet cell antibodies and determinants such as age and HLA type. Certain characteristics, however, may be related to islet cell autoimmunity in a more complex way. There appears to be some racial difference in onset-related islet cell antibody prevalence and other autoimmunity. The observation that autoimmune abnormalities are more frequent among women and among diabetics leads to the question of whether there is an interaction of sex and autoimmune diabetes. There may be a group of early-onset patients, distinguished by persistent islet cell antibodies or coexistent autoimmune phenomena, who are predominantly female. At present, there is only limited evidence for this in the literature: Bottazzo et al. found that juvenile diabetics with persistent islet cell antibodies were more often female. Female diabetics have been shown to have an increased prevalence of thyroid autoantibodies compared with male diabetics. Several observations of differences based on sex have emerged from recent studies of insulin-dependent diabetes: 1) the HLA-DR4 antigen is more frequent among female diabetic patients; 2) male HLA-identical siblings of diabetics have a lowered insulin response to glucose administered intravenously; 3) in areas of low insulin-dependent diabetes incidence, the patterns of onset by age differ markedly between the sexes. These sex-specific differences may help to clarify the relation between islet cell autoimmunity and sex. Among nondiabetic persons, those having the highest genetic "risk" for disease appear to have an increased prevalence of islet cell antibodies. There is also some indication that HLA-DR3 may be associated with islet cell autoimmunity. Other related diseases, notably gestational diabetes, non-insulin-dependent diabetes, and certain autoimmune endocrinopathies, are associated with an increased prevalence of islet cell antibodies. An increase in islet cell antibody prevalence occurs in certain viral infections, particularly mumps and congenital rubella. Islet cell antibodies have been noted in the sera of subjects many years before the onset of insulin-dependent diabetes, as well as in normoglycemic relatives.