Ten patients, all with intractable pain due to chronic pancreatitis, were selected for treatment by lateral pancreaticojejunostomy (modified Puestow procedure) after preoperative endoscopic pancreatography in each had revealed dilatation of the main pancreatic duct. Follow-up endoscopic pancreatograms performed 1 yr after surgery show a patent anastomosis in all 10 patients. Eight of these 10 are largely or completely pain-free, but 2 continiue to have pain without improvement after the operation. Surgical success in relieving pain was accompanied neither by improvement in pancreatic function, nor by protection against its further deterioration: Whereas 2 patients had malabsorption and 3 were diabetic preoperatively, 6 had malabsorption and 5 had diabetes postoperatively. This progression of exocrine or endorine pancreatic insufficiency indicates that decompression of the dilated pancreatic duct, although an effective means for relief of pain in chronic pancreatitis, does not prevent continuing destruction of pancreatic glandular tissue.