This study compared the prevalence of sick building syndrome among two groups of public service workers in Perugia, central Italy. 525 were employed in an air conditioned building with fan-coil units in every room and 281 in three naturally ventilated buildings. All the subjects completed a questionnaire about work-related SBS symptoms with an occupational medicine specialist. The workers in the air conditioned building most commonly complained about dry air, strong lighting and high temperatures and suffered a higher prevalence of SBS symptoms than those in the naturally ventilated buildings. This was the first time that SBS has been detected in Italy. Several factors may have caused the symptoms including excessive lighting, low relative humidity, fibreglass on the floors and furniture, poor maintenance of the air conditioning plant and lack of information among the employees of the self-regulation of fan coil units.