Two diabetic children with nonketotic hyperosmolar coma were treated successfully. In one of the patients, plasma-free fatty acids, insulin, C-peptide and two lipolytic hormones (growth hormone and cortisol) were measured serially during the coma. Free fatty acids, insulin, C-peptide, growth hormone and cortisol levels were within normal ranges and subsequently these levels did not change significantly. The results suggest that the normal levels of lipolytic hormones may account for the normal plasma free fatty acids and the absence of ketosis found in children with nonketotic hyperosmolar coma, in contrast to the elevated levels of lipolytic hormones and ketone bodies in ketoacidotic diabetic coma.