Aspiration of gastric acid is one of the most feared narcosis complications. The currently practiced methods of prophylaxis did not reduce the frequency of aspiration pneumonitis. In a prospective randomised study orally and intramuscularly given Cimetidine significantly reduced the toxicity of stomach contents. The intramuscular route proved to be superior. Preoperative prophylactic use of Cimetidine can be a useful method to reduce the frequency of Mendelson's syndrome without disadvantages.