The relationship between the dosage of pancreatic extract and the excretion of uric acid was investigated in 29 patients with cystic fibrosis and exocrine pancreatic insufficiency. Urinary excretion of uric acid was normal in patients receiving small doses of pancreatic extracts and abnormally high in those receiving large amounts. In the latter group, normouricosuria was achieved by reducing the dose of pancreatic extract. Normal stool patterns and adequate weight gains were preserved by a diet modification that was well accepted by the patients. To eliminate the potential renal consequences of hyperuricosuria, it seems appropriate to control the need for increasing amounts of pancreatic enzymes by limiting the dietary intake of fat and maintaining a positive caloric and nitrogen balance with high intake of protein and carbohydrates and supplementation with medium-chain triglycerides.