45 healthy young women received 50 mg Ranitidin as soon as the anaesthetist was informed that general anaesthesia was necessary for an obstetric manoeuvre. During the procedure the gastric contents were analysed quantitatively and the pH values were measured. In the parturient women, the Ranitidin effect was not attained within thirty minutes, contrary to the results obtained in male volunteers. Neutralisation was not obtained in male volunteers. Neutralisation was not obtained in all of the patients even within sixty minutes. Hence, intravenous Ranitidin cannot prevent acid aspiration in non-elective obstetric surgery if employed as the only precaution.