Characteristics, and the occurrence of other diseases, and complications related to diabetes mellitus of 91 consecutive diabetic patients who underwent vitreous surgery in 1979-1985 were examined. The mean age of the patients was 40 years (median 37, range 19-74), and the mean duration of diabetes 23 years (range 5-44). All, but one, had insulin therapy. Abnormalities in the cardiovascular and/or renal function were found in 89 of the 91 patients (98%). Signs of cardiovascular disease were observed in 58 patients (64%): 42% had elevated blood pressure (greater than or equal to 150/100 mmHg), 46% were on antihypertensive therapy, 14% had a history or signs of ischaemic heart disease, 12% had been digitalized, 7% had a history of cerebral ischaemia, and 8% had had surgery for gangrene of the lower limb. Signs of nephropathy were recorded in 64 patients (70%); 6 of them were on dialysis therapy, and two had received a kidney transplant. Symptoms possibly related to autonomic neuropathy e.g. postural hypotension, urinary tract symptoms, and gastric discomfort were found in 27%. Nine patients (10%) had some kind of thyroid disease, and two of them signs of multiple autoimmune endocrinopathy. The percentage surviving decreased from 96% at one year to 80% after 5 years of follow-up.