Review of recent literature with emphasis on growth, development and epidemiology of eating disorders and diabetes reveals many common features of the conditions. Thus we hypothesize more concurrence than would occur by chance alone. At present epidemiological evidence is inconclusive, but prevalence of eating disorder seems increased in insulin dependent diabetes mellitus (IDDM). Over a period of 25 years five cases (all female) of diabetes were found in a consecutive series of 242 patients with eating disorders treated at the Child Psychiatric and Psychiatric Clinics at Rigshospitalet, Copenhagen, Denmark. This is a six-fold increase in prevalence of IDDM. IDDM preceded eating disorder (anorexia nervosa (AN)/bulimia(B)) in four of the five cases, and contributed significantly to the psychopathology found: the more, the earlier the age at onset of IDDM. Treatment proved difficult and the outcome seems serious. At latest contact four cases had manifest eating disorders and three of these had unstable and complicated IDDM as well. The patients' adaptation to IDDM seems crucial for the outcome.