Because sodium citrate is known to increase both gastric pH and gastric volume while metoclopramide decreases gastric volume, we evaluated, in a double-blind randomized study, the effect of combining metoclopramide with sodium citrate on gastric pH and volume after induction of anesthesia in 60 female patients to determine whether gastric pH could be increased at the same time that gastric volume was decreased. All patients received 50-ml sodium citrate. To mimic standard anesthetic practice, all patients were premedicated: 20 patients received meperidine alone, 20 received meperidine plus 20-mg metoclopramide, and 20 received diazepam plus 20-mg metoclopramide. Metoclopramide failed to decrease median gastric volume or to increase the number of patients with gastric volumes less than 25 ml. There was no difference in median pH values in the three groups of patients. In patients receiving metoclopramide, the risk of pH values less than 2.5 was greater with gastric volumes less than 25 ml than in patients with volumes greater than or equal to 25 ml. We conclude that preoperative metoclopramide does not decrease gastric volume in patients premedicated with meperidine or diazepam and that when gastric volume was less than 25 ml the neutralizing effect of sodium citrate was lost.