Between 1991-2000 2052 patients (81% men and 19% women) were referred to our Sleep Laboratory because of OSA suspision. In 1194 (58%) subjects (88% men and 12% women) diagnosis of obstructive sleep apnoea (OSA, AHI > 10) was confirmed. In 430 of them (36%) mild OSA (AHI 11-25), in 243 (20%) moderate OSA (AHI 26-40), and in 521 (44%) severe OSA (AHI > 40) was diagnosed. Epworth sleepiness scale score in those groups was 10.4, 10.5 and 13.0 points respectively. 908 (76%) of patients with OSA were submitted to nCPAP treatment. Effective CPAP pressure ranged from 5 to 20 milibars, mean 8.4 mbars. In 21 patients upper airway resistance syndrome (UARS) was diagnosed. Central sleep apnoea, most frequently of Cheyne-Stokes respiration type was diagnosed in 13 patients. The most common diseases accompanying OSA were: systemic hypertension (46%), coronary heart disease (29%), diabetes (12%), and COPD (9%). Majority of OSA patients (61%) were obese (BMI > 30 kg/m2), 32% were over weight (BMI 25-30 kg/m2). Only 7% had normal body weight (BMI 20-25 kg/m2). Long-term (more than one year) compliance to treatment was found in 70% of patients prescribed CPAP.