Diabetes mellitus caused by pancreatic exocrine disease is a unique clinical and metabolic form of diabetes. The diagnosis of pancreatic diabetes caused by chronic pancreatitis may be elusive because it is occasionally painless and often not accompanied by clinical malabsorption until after hyperglycemia occurs. Diabetic patients with pancreatic calcification or clinically demonstrable pancreatic exocrine dysfunction will manifest the unique aspects of pancreatic diabetes described herein. Like other forms of diabetes, the primary hormonal abnormality in pancreatic diabetes is decreased insulin secretion. Patients with this disorder are unique in that they have low glucagon levels that respond abnormally to several physiological stimuli, blunted epinephrine responses to insulin-induced hypoglycemia, and malabsorption. In addition, they often have concomitant alcohol abuse with hepatic disease and poor nutrition. These characteristics result in increased levels of circulating gluconeogenic amino acids, decreased insulin requirements, a resistance to ketosis, low cholesterol levels, an increased risk of hypoglycemia while on insulin therapy, and the clinical impression of brittle diabetes. Retinopathy occurs at a rate equal to that of insulin-dependent diabetes but may be less severe in degree. Other complications of pancreatic diabetes have been less well studied but may be expected to be seen more frequently as these patients survive longer. The characteristics of pancreatic diabetes suggest that a conservative approach be taken in regard to intensive insulin therapy and tight blood glucose control.