The volumes and pH of gastric juice in 26 outpatients presenting for dental surgery were measured by simple aspiration through a nasogastric tube introduced after the induction of anaesthesia. The average volume in these patients who were non-smokers was 9 ml and in those patients who had smoked on the day of the operation was 19 ml. Four of the smokers had more than 25 ml of gastric juice with a pH of 2.0 or less. It is suggested that out-patients who smoke would benefit from prophylaxis such as oral antacids or metoclopramide before anaesthesia.