A reproducible model of diabetic state was produced by resecting more than 90% of the pancreatic tissue in Wistar strain male rats. Five rats with diabetic state after the resection received islet transplantation into the liver through the portal vein. All these five rats showed normoglycemia one week after the injection and it lasted about six months. A morphometric analysis using 1190 serial sections of the control rat pancreas showed that the islet distribution accorded satisfactorily with Weibull and gamma distribution, when an islet was regarded as a sphere in the three dimensional space. The estimated value of radius and number of the islets was 0.0155 mm and 131.2/mm3, respectively, whereas volume fractions of the islet tissue in the splenic and gastric segments, and parabiliary and duodenal segments were estimated at 1.45 and 0.98%, respectively. The mean half of the largest diameter of the isolated islets under dissecting microscope reached to 0.080 mm and 500 isolated islets account for about 14% of volume fraction in a whole pancreas. As the remnant pancreas possibly had approximately five percent of islet volume, the transplanted animal contained about 19% of islet volume as compared to the control animal. It could be concluded that transplantation of 500 islets controlled diabetes in the rat with subtotal pancreatectomy. But the transplanted rats eventually became diabetic about six months after the transplantation possibly because of insufficient volume of implanted islets.