The comparative effect of a 50% proximal or distal enterectomy on the exocrine pancreas and the remaining intestine has been studied in the rat one month after operation. Distal enterectomy induces (1) growth of the pancreas, characterized by a parallel increase in pancreatic weight, protein, DNA, RNA, amylase, lipase and chymotrypsin content, (2) preferential adaptation of the remaining ileum. Proximal enterectomy did not modify the pancreatic parameters studied but brings about an adaptation of the duodenum, the remaining jejunum and the ileum. It is concluded that pancreatic and intestinal adaptations differ after proximal and distal enterectomy.