Pancreatic exocrine and endocrine function was assessed in four patients 4-31 months after 88%-95% pancreatectomy. Postoperative exocrine and endocrine function was not seriously impaired. Extensive pancreatic regrowth occurred. The amount of regenerated pancreatic tissue, estimated by sonographic measurement of the sectional area, was not significantly different from that of healthy controls. Pancreatic endocrine and exocrine function and pancreatic regeneration remained satisfactory and no additional pancreatic resection became necessary. These results indicate that 95% pancreatectomy may be tolerated without loss of pancreatic function.