The splanchnic nerves are inevitably stimulated during upper abdominal surgery and this may produce various responses. To assess the role of splanchnic nerve stimulation on the endocrine-metabolic responses to abdominal surgery, intra-operative splanchnic nerve blockade was carried out in 12 patients undergoing elective gastrectomy under general anaesthesia and the results compared with those of patients undergoing gastrectomy under general anaesthesia or epidural analgesia alone. In the splanchnic blockade group, intra-operative increase in plasma cortisol, glucose, FFA (free fatty acids) and urinary adrenaline excretion were significantly less than that of the general anaesthesia group. This inhibitory effect of splanchnic blockade on these endocrine-metabolic responses was almost the same as, but slightly less remarkable than, that of high spinal epidural blockade. Urinary noradrenaline excretion reached the highest level on the first postoperative day in the general anaesthesia group. This noradrenaline response was significantly inhibited in the splanchnic group as well as in the epidural group. These results appeared to indicate that mechanical stimulation to the splanchnic nerve due to operative manipulation is largely responsible for the endocrine-metabolic responses in abdominal surgery. The results also suggested that, in addition to the splanchnic nerve stimulation, conscious pain perception is responsible for catecholamine release.