Objectives. Our objective was to study the clinical effectiveness of promethazine in the prevention of epidural morphine-induced pruritus in cesarean section. Methods. A prospective randomized double-blind placebo-controlled study, 60 ASA I-II patients undergoing Cesarean section under epidural anesthesia with 15-25 ml of 2 % lidocaine with 1 : 200,000 adrenaline. After the delivery of a newborn, each patient received epidural injection of 4 mg of morphine via epidural catheter. Simultaneously, patients were randomly divided into 2 groups to receive intramuscular injection of 1 ml of normal saline in placebo group respectively. In the postoperative period, the pruritus and nausea/vomiting were assessed every 2 hours for 48 hours. Twenty five mg of oral diphenhydramine was also administered as required for the treatment of pruritus during the study. Results. There was no statistically significant differences in the demographic data, the incidence and severity of pruritus. The incidence of pruritus was 76.7 % in placebo group and 60 % in promethazine group. The intensity of pruritus was 3.7 ± 2.6 and 2.6 ± 2.4 in placebo group and promethazine group respectively. The diphenhydramine requirement for treatment of pruritus showed to increase significantly in placebo group (17.4 ± 29.6 mg/patent) as compare to promethazine group (8.3 ± 19.2 mg/patient). Additionally the nausea/vomiting in placebo group (30 %) had a higher incidence than that in promethazine group (3.3 %). Conclusion. Intramuscular promethazine could not prevent the epidural morphine-induced pruritus in this study. However it appeared to reduce the diphenhydramine requirement for the treatment of pruritus and incidence of nausea/vomiting in patients undergoing Cesarean section with epidural morphine anesthesia.