This study supports the premise that cimetidine would be an effective agent in the prophylaxis of aspiration pneumonitis and has several advantages over the usual antacids. It is more palatable, increases gastric pH more consistently than Maalox, and has longer duration of action. Although the drug may be advantageous for women in labor, the authors are unaware of any study of its acute effects on either labor or the fetus. Since there is no known hazard to single-dose administration of cimetidine, it is suggested that it be given 'routinely' in a dose of 300 mg orally two hours prior to induction of anesthesia in all surgical cases.