An unselected sample of 46 female adolescents with insulin-dependent diabetes mellitus (IDDM) for more than one year were assessed systematically for the presence of anorexia nervosa and bulimia. These disorders and their partial syndromes were found in 19.5% of this population. Anorexia nervosa and bulimia diagnosed on the basis of DSM-III criteria were each found in 6.5% of the population representing approximately a 6-fold and 2-fold increase respectively in the expected prevalence for similar nondiabetic individuals. Bulimic symptoms were associated with poor metabolic control as reflected in blood levels of glycosylated hemoglobin (HbAl). These findings have important implications both for the pathogenesis of anorexia nervosa and bulimia and for the management of some cases of IDDM with unstable metabolic control.