Background : Nausea and vomiting during spinal anesthesia for Cesarean section are common. These symptoms are distressing to the patient and disturbing the surgeon. A controlled prospective study is described which re-evaluated the safety and efficacy of intramuscular ephedrine in spinal anesthesia for Cesarean section. Objective : to determine whether intramuscular ephedrine simultaneously with induction of spinal anesthesia for non-emergency cesarean section reduce the incidence of maternal nausea and vomiting. Study design : double-blinded, placebo-controlled trial. Setting : Obstetric unit of Srinagarind hospital, Faculty of Medicine, Khon Kaen University. Subjects : 66 normotensive, ASA class I or II women with term, uncomplicated, singleton pregnancies were include in this study. Methods : The 66 patients (22 in each group) were given either placebo (control group), 15 mg or 30 mg ephedrine intramuscular. The parameters recorded : 1) blood pressure 2) heart rate 3) ephedrine intravenous supplementation 4) neonatal Apgar scores 5) nausea and vomiting symptom. Difference between groups were analyzed by Fisher's Exact test. Significance was determined at p<0.05. Results : The incidence of nausea vomiting in control group was 45.5 which was not significantly different from the incidence of 54.5 and 36.4% in the both treated group. Conclusion : Prophylactic intramuscular ephedrine does not reduce the incidence of maternal nausea and vomiting after spinal anesthesia for non-emergency cesarean section.