Good quality, long lasting pain relief can be achieved with intrathecal opiates, but often at the expense of pruritus, nausea and vomiting. Two groups of patients undergoing caesarean section under spinal anaesthesia with heavy bupivacaine 0.5% plus 0.2 mg preservative-free intrathecal morphine were studied. Patients were randomly selected to receive an infusion of dextrose saline with or without naloxone at 0.1 mg/h (over 8 h) after delivery of the baby and were studied for 24 h to assess analgesic requirements and side-effects. There was a significant reduction in the frequency and severity of pruritus in the naloxone group while the infusion was running, but pain relief was not impaired.