BACKGROUND: To decrease the risk of pulmonary aspiration of gastric contents, patients are routinely asked not to eat or drink anything for at least 6 to 8 hours before surgery. We studied to evaluate whether the volume and pH of gastric fluid immediately after induction of anesthesia is correlated with water ingestion. METHODS: Fifty patients, scheduled for elective surgery, were randomly divided into two groups. Control group(n=25) were fasted overnight and received no water. Experimental group(n=25) were fasted overnight and received 150 ml water approximately 2 hours before the induction of anesthesia. Gastric fluid was obtained via multiorifice gastric tube with the patient in three different positions. The volume of gastric fluid was recorded and its pH was measured. RESULTS: The gastric volumes were no differences between the two groups. The gastric pH values were significant differences. The incidence of patients with the high risk factors of gastric volume greater than 25 ml and pH less than 2.5 was decreased in experimental group. CONCLUSIONS: We concluded that surgical patients could be permitted to ingest 150 ml water approximately 2 hours before the induction of anesthesia.