We report the results of a study comparing two dose regimens of the gastric antisecretory agent, omeprazole, used as prophylaxis against pulmonary aspiration of gastric contents during general anaesthesia for elective Caesarean section. Since antisecretory agents do not clear stomach contents already present at the start of treatment, two groups of patients who had received both omeprazole and a prokinetic drug, metoclopramide, were also studied. Thirty patients received oral omeprazole 40 mg on the evening before and on the morning of the operation (group 1), 33 received oral omeprazole 80 mg on the morning of the operation (group 2), and 15 (group 3) and 16 (group 4) patients respectively received the oral omeprazole doses stated above and in addition metoclopramide 10 mg given intramuscularly at least 20 min before induction of anaesthesia. Gastric aspirate pH and volume were measured at induction of anaesthesia and on completion of surgery. At induction of anaesthesia, treatment was judged successful (pH > or = 2.5 and volume < 25 ml) in 87%, 73%, 100% and 81% of patients in groups 1-4 respectively. The corresponding results on completion of surgery were 100%, 88%, 100% and 100%. While omeprazole is useful as prophylaxis against pulmonary aspiration during general anaesthesia for elective Caesarean section, the addition of a prokinetic agent seems to be necessary to maximise its effects.