SUMMARYDuring the course of anaesthesia and surgery in South India, it was noticed that Indian and European patients responded differently. In an attempt to evaluate these differences, blood sugar values were used as a guide to the sympathetic nervous response. Under general anaesthesia values rose and stayed higher in Indian patients than in Europeans in India or England. General anaesthesia by itself provoked no elevation until the commencement of surgical trauma. Under subarachnoid or epidural analgesia, no major change in blood sugar occurred during surgery. During the study involving 141 patients, three collapsed unexpectedly and resuscitative measures invalidated the blood sugar results. Although nutrition might play some part, the differences are considered to be racial and not climatic.