Two pancreatic chambers constructed of plastic tube and ultrafiltration membrane and containing the minced pancreases of five neonatal rats were implanted in the omentum of totally pancreatectomized diabetic dogs. Blood glucose levels in the diabetic dogs leveled off just after operation, in contrast with those in control animals, in which vacant chambers were implanted, and began to decrease about a week after the transplantation. Blood glucose levels fell to less than 150 mg/100 ml within three weeks. The neonatal rat pancreases in the pancreatic chamber produced a near normal plasma glucose and insulin response to an intravenous glucose tolerance test on the 20th day after transplantation. Removal of the pancreatic chamber from the experimental dogs after normalization of blood glucose levels, caused a rapid elevation of blood glucose levels, and lead to death within four days. No rejection reactions were observed in the course of the experiment. These findings suggest that pancreatic transplantation with the pancreatic chamber is potentially useful for the treatment of diabetes.