A new method of eliminating the exocrine function of the pancreas by obstruction of pancreatic duct with neoprene was investigated in dogs and applied to three cases of human segmental pancreatic transplantation. Neoprene is a liquid synthetic rubber which flocculates with changes in pH. In animals, progressive fibrosis of the pancreatic tissue occurs after injection of neoprene in the main pancreatic duct, leaving islets well vascularized and functioning for prolonged periods. Using this technique, three severely diabetic patients received a cadaver segmental pancreatic allograft. Blood sugar returned to normal levels within the first hours or days after operation. All three grafts continue to function 1.5, 2, and 8 months, respectively, following transplantation. If these results are confirmed by further clinical experience, this method may be of considerable assistance in the treatment of severe diabetes by pancreatic transplantation.