The injection of neoprene into the pancreatic ducts appeared to be a simple and effective means of suppression of the pancreatic exocrine function in dogs. It was investigated in experiments performed in three groups of dogs the pancreas of which were injected with 1 to 6 ml of neoprene. In group I (injection alone), all animals showed pancreatic exocrine insufficiency, none was diabetic. In group II, the dogs received a substitutive treatment and a special diet, they survived in a good general condition up to the time of sacrifice. There was extensive pancreatic fibrosis with disseminated Langerhans islets. In group III, a cephalic pancreatectomy was performed after the injection of neoprene into the pancreatic ducts, 8 animals were alive and well after 3 to 15 months, and showed a normal level of blood sugar, insulin, glucagon and amylase without glycosuria.