BACKGROUND: Aspiration of gastric contents is one of the most feared complications during anesthesia. But the routine preoperative order "NPO after midnight" produces thirst, hunger, irritability and other unpleasant experiences in elective inpatients. So, we evaluated the effect of preoperative clear fluid (orange juice) intake, with and without ranitidine, on gastric volume and pH. METHODS: Sixty unpremedicated adult patients, ASA class I or II, scheduled for elective operation were randomly divided into three groups. Group I (n = 20) fasted after midnight. Group II (n = 20) ingested orange juice 150 ml, 2 3 hours before anesthesia. Group III (n = 20) ingested orange juice 150 ml with ranitidine 150 mg, 2 3 hours before anesthesia. As soon as the patients were intubated and stabilized after induction, gastric contents were collected via 16 18 French Salem Sump tube. Gastric volume and pH were measured. RESULTS: Statistically significant differences were found between groups I and II on the hand and group III on the other, in both of gastric volume and pH. But there were no significant differences between groups I and II. CONCLUSIONS: These results suggest that preoperative clear fluid intake does not affect gastric volume and pH. Moreover, concomitant administration of ranitidine decreases gastric volume and increases pH.