Fifty-nine patients with chronic pancreatitis were studied in retrospect. The incidence of overt diabetes was high, 36/59. Half of the diabetics were insulin-dependent, and among these labile diabetes with hyperglycemia and high amounts of glucose in the urine was not uncommon. Hypoglycemic episodes were noted in 14 of the 18 insulin-treated patients, and in 3 patients severe hypoglycemia was believed to be the cause of death. Mechanisms leading to such disastrous hypoglycemia are discussed, and a hypothesis regarding lack of glucagon as the cause of severe hypoglycemic attacks was experimentally tested by measuring pancreatic glucagon in plasma in two patients with pancreatic diabetes and severe brain damage following hypoglycemic coma. Low basal glucagon values were found, and the normal rise upon insulin-induced hypoglycemia was not seen. From these results it may be justified to suggest, firstly that glucagon should be used in the management of severe hypoglycemia in chronic pancreatitis, and secondly that a certain degree of hyperglycemia should be allowed in the treatment of diabetes in these patients.