The short-term therapeutic effect of oral hypoglycaemic agents has been assessed in 12 patients with symptomatic diabetes secondary to chronic pancreatitis (pancreatic diabetes). In six patients who had moderate to severe carbohydrate intolerance, associated with severe insulinopaenia during arginine infusion, the potent sulphonylurea chlorpropamide produced no change in the fasting blood glucose level after two weeks of treatment. This contrasted with the significant reduction produced in a matched group of maturity-onset primary diabetics. The six patients with milder diabetes, and a greater (although still subnormal) insulin secretory capacity, showed an improvement in oral glucose tolerance during the first hour following glucose administration while on chlorpropamide. When the biguanide phenformin was substituted for chlorpropamide in five of these patients, a statistically insignificant improvement in glucose tolerance was observed during treatment. Applications of these findings to the practical management of pancreatic diabetes are briefly considered.