A review if presented of the use of low-dose insulin infusion in the management of 58 episodes of severe diabetic hyperglycaemia. Neutral insulin in a dosage of 2-4 units per hour is infused via a paediatric giving set to achieve a sustained physiological elevation of insulin levels. This method is safe, simple and rapidly effective in lowering the blood glucose level, the mean rate of fall (62 mg/100 ml/hr, or 11% per hour) being unaffected by prior insulin therapy, acidosis or ketonuria. Classification of the hyperglycaemia as ketoacidotic or hyperosmolar is unnecessary before insulin therapy is instituted, as the relative decline in glucose level is the same in the hyperosmolar non-ketotic group as in the others. Proven infection significantly lowers the rate of fall of glucose level. Hypoglycaemia and hypokalaemia are rare during low-dose infusion. Early and adequate replacement with potassium phosphate is recommended, oral potassium supplements being continued for several days. Bicarbonate therapy is rarely indicated in the management of acidosis. No patient had cerebral oedema during treatment, and one elderly patient with extensive pneumonia and empyema died during the infusion. It is suggested that continuation of low-dose insulin infusion, together with 5% dextrose solution, after the plasma glucose level reaches 200 mg/100 ml, may hasten the clearance of ketones, preventing relapse.