Ligation and section of the main and accessory pancreatic ducts were performed in adult mongrel dogs. Four weeks after the procedure we carried out total pancreatectomy in six duct-ligated dogs, and an attempt was made to prepare the graft of islets from the highly scarred pancreas of the duct-ligated dogs by means of a newly developed collagenase perfusion method. We succeeded to normalize the high fasting glucose level which occurred after the total pancreatectomy in three of six dogs through the autotransplantation of the procured graft. However, insulin secretion was severely depressed in transplanted animals. Two of the three dogs showed high plasma glucose levels 15 and 20 weeks after the transplantation, respectively. Histological examination of the spleen revealed well preserved islets with good immunocytochemical insulin staining in one transplanted dog whose plasma glucose level was controlled for about five months. No pancreatic exocrine tissue was detected in the histological sections of the spleen in the transplanted dogs and in a transplanted control dog.