We considered data of samples collected in the period 1994-2001 in 83 operating rooms of 13 different public and private hospitals in Veneto Region. The anaestetic gases more used in operating rooms were nitrous oxide, isoflurane and, more recently, sevflurane. The mostly polluted positions were those in proximity of anaesthesiologic devices; the gases average concentrations were low in all hospitals examined, although some operating rooms demonstrated concentrations of anasthetic gases exceeding limit values. Lastly, the professional figures had different exposure to the various anaesthetic gases.