A clinical study of the use of intrathecal morphine in two groups of surgical patients, 32 in all, showed that the morphine provided very powerful and prolonged analgesia with little disturbance of cerebral function. When combined with a spinal block it did not interfere with the action of the spinal anaesthetic. When combined with a relaxant technique of anaesthesia some persistent curarisation was seen. The only complication to emerge from the study was respiratory depression which could be very delayed in its offset. The depression was sufficient to induce carbon dioxide narcosis in two patients. It is suggested that the dose of intrathecal morphine in the very elderly should be very severely restricted as they appeared to be unduly sensitive to the respiratory depressant effect of morphine when given intrathecally.