BACKGROUND: Aspiration of gastric contents is an ever -present risk in the use of general anesthesia, particularly in emergency and obstetric situations, and morbidity and mortality associated with this complication increases with the volume and acidity of the aspirate. Since direct inhibition of acid secretion may be a preferable method, we studied the effectiveness of ranitidine in increasing gastric pH. METHODS: Sixty patients scheduled for elective cesarean section under general anesthesia before midday were randomly divided into three groups. The control group (n=20) did not received preanesthetic ranitidine. Group I (n=20) received a slow intravenous injection of 50 mg ranitidine, one hour before surgery. Group II (n=20) received 150 mg ranitidine orally, both the night before surgery and the morning of surgery. RESULTS: Compared with the control group, the mean gastric pH increased significantly in group I and II (P<0.05). There was no significant difference of gastric pH between group I and II. CONCLUSIONS: The results of this study indicate that ranitidine is a useful agent in increasing the gastric pH in women undergoing elective cesarean section. Ranitidine administered intravenously and orally were equally effective means in increasing the gastric pH.