The effect of low-dose insulin infusion (4.8 U/h) in diabetic ketoacidosis was compared to that of low-dose insulin infusion (4.8 U/h) plus somatostatin (500 microgram/h IV). Treatment with insulin only in 20 patients caused normalization of blood glucose levels within 6 hours and resolution of ketoacidosis within 5 hours. During insulin plus somatostatin infusion in 7 patients, blood glucose levels returned to normal within 4 hours and acidosis was reduced within 3 hours. Correction of acidosis is the most important problem in diabetic ketoacidosis: in the severest cases cardiovascular and cerebral complications may ensue. The data presented show that addition of somatostatin to treatment with low doses of insulin reduces and resolves acidosis in a shorter time while plasma levels of glucagon and GH were concomitantly reduced.