In a retrospective study, we analyzed the prevalence of diabetes-associated late complications in 549 type 1 (insulin-dependent) diabetic patients who have been treated at the University Hospital of Ulm between 1980 and 1987. Retinopathy, proteinuria and neuropathy depended on the duration of the disease, whereas age was the major determinant of large vessel disease. After 20 years of diabetes, 85% of the patients showed retinopathy, half of them proliferative retinopathy, 52% had persistent proteinuria (greater than 500 mg/day), 20% of them were under dialysis. 74% of the patients showed signs of peripheral and/or autonomic neuropathy, 19% had manifestations of large vessel disease. There was no consistent correlation between the levels of glycosylated hemoglobin and the occurrence of diabetic late complications. However, hypertension was closely associated with both small and large vessel disease.