This study was undertaken to quantify the exposure of operating room staff to nitrous oxide during routine paediatric otolaryngeal surgery and to determine the influence of the method of induction of anaesthesia on this exposure. The nitrous oxide exposure of the anaesthetist, the surgeon and the circulating nurse were measured, using body-worn passive atmospheric samplers, during twelve routine paediatric otolaryngeal surgical lists. During six of the lists an inhalational technique, with nitrous oxide, oxygen and halothane, was used for the induction of anaesthesia. During the other six lists anaesthesia was induced using intravenous thiopentone. In all cases, anaesthesia was maintained using nitrous oxide, oxygen and halothane. Regardless of the induction technique used, the mean nitrous oxide exposures of the anaesthetist, the surgeon and the nurse all exceeded the maximum level of 25 ppm.hr-1 recommended by the United States National Institute for Occupational Safety and Health (NIOSH). The use of an intravenous technique for the induction of anaesthesia reduced the nitrous oxide exposure of the anaesthetist and the circulating nurse. This suggests that, although the use of an intravenous induction may reduce exposure to nitrous oxide, the NIOSH recommendations for maximum exposure of operating room personnel to nitrous oxide are currently unattainable in practice.