Obstructive Sleep Apnea syndrome (OSAS) is largely prevalent among the general adult population, particularly among obese subjects. Diurnal somnolence is a characteristic feature of OSAS, one that can interfere on daily life of the patients and also on his/her work-related activities. Aim of this study was to evaluate the impact of OSAS, its symptoms and its therapy with Continuous Positive Airway Pressure (CPAP) may have on work-related activities. Fourty-eight subjects were studied, all > 18 years old and in a work-related age (< 65 years for men, < 60 years for women). There were 34 males and 14 females, 38 actively working, 3 unemployed, 7 not actively working. Before diagnosis the Epworth Sleepiness Scale (ESS) was 12 +/- 4, after the use of CPAP it was 4 +/- 4 (p< 0.001), the Apnea Hypopnea Index (AHI) before CPAP use was 44 +/- 24, after CPAP use 4 +/- 4 (p< 0.001). CPAP compliance was very good (mean hours of CPAP/night 5 +/- 2). At yearly follow-up, work activity was confirmed in all patients, as all employed patients were still working. Our data seem to indicate that not only OSAS interferes with working performance, mainly due to OSAS-related diurnal somnolence, but also that appropriate CPAP therapy, reinforced with educational activities and followed after one year, is able to ameliorate OSAS-related symptoms, potential cause of inefficiency an occupational risk at work.