During the past decades insulin has been given in relatively high doses when treating diabetic coma. Recently low-dose insulin treatment has been proposed by several groups. In the reported investigation insulin was initially given in moderate to high doses (12-200 U/h) with a steady reduction in dose during the course of treatment. Insulin infusion was regulated either manually with an adjustable infusion pump (7 patients) or automatically with an artificial endocrine pancreas (glucose-controlled insulin infusion system; 11 patients). Thus 18 patients with decompensated diabetes mellitus (coma or precoma) were treated. In 14 patients with ketoacidotic decompensation laboratory data on hospital admission were: blood glucose 7.35 +/- 0.61 g/l, serum potassium 4.7 +/- 0.4 mmol/l, pH 7.1 +/- 0.04, base excess - 19,7 +/- 2.2 mmol/l (x +/- SEM). The other patients had hyperglycaemic or hyperosmolar non-ketotic decompensation. In all patients controlled reduction of blood glucose levels was achieved within 2.3 to 18 hours. The amounts of insulin infused during this ranged from 17 to 320 units, but in one instance was 1950 units. There were no complications.