INTRODUCTION: As occupational exposure to anaesthetic gases is one of the main risks for operating theatre staff an environmental monitoring campaign was conducted in order to evaluate the degree of pollution by nitrous oxide (N2O) in the operating theatres of some hospital facilities in Liguria. METHODS: Any leaks (systemic and/or managerial) of anaesthetic gas and the number of efficacious air exchanges per hour supplied by air-conditioning systems were evaluated by means of an IR spectrometer, which was wired to a computer for data collection and analysis. The concentration of nitrous oxide in the centre of each operating theatre was measured by means of chemo-adsorbent cartridges analysed by gas chromatography. RESULTS: In 76.0% of the operating theatres examined a mean environmental concentration of N2O below the legal limits was recorded. The highest mean concentrations were generally associated with the presence of systemic leaks. Supplying an adequate number of efficacious air exchanges per hour enabled environmental concentrations of anaesthetic gas to be kept within acceptable levels. DISCUSSION AND CONCLUSIONS: Training personnel in the correct management of the operating theatre and of anaesthesia equipment, and ensuring the availability of an adequate air-conditioning system enable the risk of exposure to nitrous oxide to be minimised. This can be achieved through a concerted effort on the part of all involved, in accordance with the concept of ongoing improvement in healthcare services.