The effects of an extradural narcotic, diamorphine, and of an extradural local anesthetic, bupivacaine, on postoperative responses of plasma glucose and cortisol levels following surgery were investigated in 20 fit women undergoing major gynecologic operations. The operations were conducted with morphine premedication and extradural local anesthetic with nitrous oxide, oxygen, and halothane. After surgery the patients were given either further extradural local anesthetic or 5 mg of extradural diamorphine. After surgery plasma glucose and plasma cortisol concentrations decreased in patients given extradural diamorphine, but increased in those given extradural local anesthetic. The differences between the groups were statistically highly significant (p less than 0.05) for both glucose and cortisol. The effects on metabolic responses to surgery produced by a small (5 mg) dose of diamorphine injected into the extradural space suggest a local action of the narcotic at the level of the spinal cord. Only very large intravenous doses of narcotics have previously been shown to suppress these responses.