Abstract Review of the thirty year experience at the Lahey Clinic with 530 cases of chronic pancreatitis shows that the clinical, physiologic, and pathologic manifestations of the disease are extremely varied and indicates that the most significant feature in the treatment of these patients is the choosing of the appropriate operation for each individual patient after careful exploration of the pancreas. The progressive and irreversible structural changes include fibrosis, atrophy, cystic degeneration, patchy necrosis, abscess formation, and pancreaticolithiasis, often with complete or partial obstruction of the pancreatic ducts. Because duct obstruction is the main pathophysiologic change, early operations directed to the biliary tract, stomach, and autonomic nervous system were generally unsatisfactory, especially in patients with advanced chronic pancreatitis. In contrast, satisfactory longterm results were obtained in 70 per cent of patients who had operations directly on the pancreas. These procedures included drainage of associated pancreatic cysts and abscesses, transduodenal decompression of pancreatic ducts, transpancreatic ductal decompression, distal pancreatectomy, pancreaticoduodenectomy, and total pancreatectomy. Unsatisfactory results were related to choice of an inappropriate operation, inability of the patient to free himself from alcoholism, and persistence of residual pancreatic inflammatory disease. The clinical antecedents of the disease, the metabolic consequences, and the results of various operations are discussed.