In a prospective controlled study 63% of 150 children without prophylaxis were at risk of aspiration pneumonia in case of aspiration or regurgitation. In a second trial 10 mg/kg cimetidine orally 120 to 180 minutes prior to induction of anaesthesia proved to be a very effective prophylaxis. In small children up to 15 kg rectal application of 40 mg/kg cimetidine was even more effective than 10 mg/kg orally in reducing gastric volume. Premedication with cimetidine may be a practicable method for reducing the risk of aspiration pneumonia in paediatric anaesthesia.