The aim of the study was to assess the clinical picture of patients with obstructive sleep apnea (OSA) and to investigate the long term effectiveness of treatment with continuous positive airway pressure (CPAP). 170 subjects were investigated with Mesam 4 screening device. Full polysomnography was performed in suspected patients confirming the diagnosis (AHI > 10) in 72 cases (69M, 3F), mean age 46.7 +/- 8.4 yrs, mean weight 110 +/- 19 kg. Snoring (100%) apneas (96%), excessive daytime sleepiness (98%) and nocturia (73%) were the most common symptoms. Application of CPAP therapy resulted in elimination of apneas, improvement in sleep architecture and in arterial blood oxygen saturation. Apnea index decreased from 63 +/- 22 to 4 +/- 4. First night compliance to CPAP was about 95%. OSA symptoms rapidly regressed. Follow-up examination was performed in 45 patients who used CPAP for more than 1 year. All subjects presented with improvement in quality of life, all but one were using CPAP almost every night (mean 6.6 +/- 0.9 night per week). The most common side effects of CPAP were uncomfortable nose mask (42%), throat dryness (27%) and eye irritation (24%) We concluded that CPAP treatment in OSA occurs to be effective, long term compliance is high, side effects are benign and mostly due to poorly fitting mask.