Sixty-two patients were given morphine 2 mg and 69 patients were given diamorphine 0.5 mg by either the epidural or intrathecal route. All had undergone either total hip replacement or spinal disc surgery. Forty-nine out of 131 patients required no further analgesia. Diamorphine was superior to morphine and the intrathecal route more effective than the epidural. Headache, pruritus, urinary retention and nausea and vomiting were recorded, the incidence of the latter being unacceptably high, particularly when the drugs were administered by the intrathecal route: one patient required resuscitation. It is suggested that previously reported respiratory depression using these techniques is associated with the administration of other analgesics contemporaneously; that dosage should be limited to one-fifth of the estimation intramuscular dose; and that patients should be observed in a recovery ward for 24 hours.