We assessed the possibility of improvements in the management of the potentially fatal acute hyperglycaemic complications of diabetes by a review of all deaths in patients who presented to the Alfred Hospital, Melbourne, with diabetic ketoacidosis or hyperosmolar coma during the 16 years, 1973-1988. All late deaths of patients during hospitalization were included in the mortality data. In the 610 episodes of diabetic ketoacidosis (pH, 7.30 or lower) or hyperosmolar coma (osmolality, 350 mOsmol/kg or greater), only one death occurred as a result of the acute metabolic disturbance--in a patient who had suffered a cardiac arrest before admission to hospital. The over-all mortality rate was 6.2% (38 deaths). The mortality rate was 4.9% (26 deaths) for 528 episodes of diabetic ketoacidosis and 14.6% (12 deaths) for 82 episodes of hyperosmolar coma. Patients with diabetic ketoacidosis who died were older than were those who survived (64 +/- 13 years compared with 40 +/- 21 years, respectively; P less than 0.001). Mortality in patients with hyperosmolar coma did not relate to age, initial blood-glucose level or osmolality. Twelve deaths resulted from bacterial pneumonia and two deaths resulted from aspiration pneumonia. Other major causes of death were mesenteric and iliac thromboses (six cases), myocardial infarction (eight cases) and cerebral haemorrhage (two cases). Of the 26 deaths that were associated with diabetic ketoacidosis, only two deaths--as a result of aspiration pneumonia and bowel infarction, respectively--were assessed as potentially avoidable after the patient's admission to hospital. Eight of the 12 hyperosmolar-coma-associated deaths occurred in newly recognized diabetic patients in whom there were avoidable delays in diagnosis. We conclude that further improvements in outcome will be difficult to achieve, but that efforts should be directed towards the earlier diagnosis of diabetes and the earlier recognition and treatment of associated acute pulmonary and vascular complications.