OBJECTIVE To search for the optimal dosage of nalbuphine relief of intrathecal-morphine induced pruritus after caesarean section. METHODS Ninety parturients who developed moderate to severe pruritus caused by intrathecal morphine after caesarean section were randomly allocated into 3 groups receiving 2, 3 and 4 mg of intravenous nalbuphine respectively. The improvement of pruritus and adverse effects of nalbuphine such as increasing pain scores, nausea, vomiting, sedation and respiratory depression were evaluated at 15 minutes after nalbuphine administration. RESULTS Percentage of successful treatment of pruritus with 2, 3 and 4 mg, nalbuphine were 86.7, 96.7 and 100, respectively (p = 0.12). There was no statistically significant difference in adverse effects. No evidence of respiratory depression was detected. However, there was significant increase in pain scores in group of 4 mg nalbuphine (p = 0.004). CONCLUSIONS Nalbuphine of 2 to 3 mg was considered to be adequate in treatment of intrathecal morphine induced pruritus after caesarean section without increasing pain scores or causing other side effects.