To investigate the effect of surgical stress on the endocrine pancreas, we evaluated the changes in glucose-stimulated insulin release from the isolated perfused pancreas 4 and 7 days after laparotomy. Four days after laparotomy, insulin response to a glucose load was poor, and integrated insulin release was significantly less in the first and third phase of stimulation than in the normal rats. At 7 days, however, insulin response to a glucose load was augmented, and the integrated insulin release was significantly increased in all the phases of stimulation. These results indicate that in the early phase after surgical stress there is an impaired insulin response to a glucose load and that in the recovery stage after surgery, there is an augmented insulin response to a glucose load.