The aim of this study was to assess the antipruritic efficacy of subcutaneous naloxone following intrathecal morphine administration. Fifty women undergoing elective Caesarean section using spinal anaesthesia were randomly allocated, in a double-blind study design, to receive either naloxone 400 microg or placebo as a subcutaneous injection at the end of surgery. Spinal anaesthesia was performed using 0.5% hyperbaric bupivacaine, 25 microg fentanyl and 150 microg of preservative-free morphine sulphate. The primary outcome measures were: incidence of pruritus, nausea and vomiting, and quality of analgesia. The incidence of pruritus and nausea and vomiting was not significantly different between the two groups. There was also no significant difference in postoperative analgesia between the two groups. We conclude that pruritus, following intrathecal fentanyl 25 microg and preservative-free morphine sulphate 150 microg, is not reduced by the addition of naloxone 400 microg administered subcutaneously on the completion of surgery.