Sixty-four insulin-dependent (Type 1) diabetic patients (IDDM) in Soweto, South Africa were followed over a 10-year period. Patients were assessed in 1982 and again in 1992. There were 10 deaths (16%), half of which were due to renal failure. Ketoacidosis, hypoglycaemia, and sepsis accounted for the rest. At the 10-year follow-up mean age (± SD) was 32.4 ± 5.0 years and diabetes duration 13.6 ± 2.6 years. Retinopathy affected 52%, peripheral neuropathy 42%, and nephropathy 28% (all significantly increased from the 1982 assessment). Microalbuminuria and autonomic neuropathy were also common. Serum cholesterol was over 6.5 mmol I−1 in 19%, hypertension affected 22%, and 28% were cigarette smokers; though no patient had evidence of macroangiopathy. We conclude that IDDM in South Africa is associated with excess mortality, a significant proportion of which is related to nephropathy. Diabetes of long duration is now not uncommon in South Africa, and although diabetic complications frequently occur, most patients have good life quality and freedom from large vessel disease.