The study aim was to investigate the effect of three different morphine doses added to levobupivacaine 0.125% for caudal analgesia after circumcision surgery in children, particularly in relation to the frequency of postoperative vomiting within the first 24 hours following surgery. Two hundred and forty patients aged 5 to 12 years undergoing circumcision were included in the study. Following induction, caudal 0.125% levobupivacaine 0.5 ml/kg was given after adding 7.5, 10 or 15 µg/kg morphine. The postoperative incidence of vomiting was 5%, 12.5% and 17.5% in the groups 7.5, 10 and 15 µg/kg morphine, respectively (P=0.012, 7.5 versus 15 µg/kg groups). Five percent of the 7.5 µg/kg group and none of the patients in the other groups required paracetamol within the first 12 hours, and there was a significantly greater need for rescue paracetamol over the 24 hours in the 7.5 group versus the 15 µg/kg group (P=0.013). Postoperative analgesic durations were long and did not differ between groups (1273±338, 1361±192 and 1426±48 minutes, respectively, P=0.08). In conclusion, because the incidence of vomiting is very low, the duration of postoperative analgesia is long and a dose of 7.5 µg/kg caudal morphine is much lower than doses previously reported to be associated with respiratory depression, this study supports the use of 7.5 µg/kg caudal morphine added to 0.125% levobupivacaine for circumcision surgery.