We investigated the compliance, effects and side effects of nCPAP in 27 patients with obstructive sleep apnea syndrome, 26 of whom filled in a mailed questionnaire. Mean treatment time was 20 months (range 1-46 months). 24 patients (92%) still used their nCPAP. 15 patients (63%) used nCPAP six or seven nights per week, and 19 patients (79%) at least three nights per week. The effect was best and the use more frequent in patients with more than nine oxygen desaturations per hour during one night. Mean body weight was reduced from 103.5 to 100.9 kg (p = 0.01). Improved professional performance and interpersonal relationships were reported, each in ten persons. 19 patients stopped snoring and no longer felt sleepy during the day. The main reasons for interruption of treatment were travelling and nasal congestion. Some help was needed to treat skin irritation and mucosal dryness. In conclusion, most patients accepted nCPAP as long term treatment and reported improvement in quality of life.