This study aimed to assess the ability of an auto-nasal continuous positive airway pressure (nCPAP) device (REM + auto; NPBFD, Nancy, France) to predict the optimal constant nCPAP level. The apnoea/hypopnoea detection facility of the auto-nCPAP device was deliberately disabled and nasal mask pressure vibration detection was the only mode of pressure setting. The auto-nCPAP device was tested on 10 previously untreated patients with obstructive sleep apnoea during a single night, with ambulatory polysomnography performed in a conventional hospital room; the efficacy of the fixed pressure determined by the auto-nCPAP device was assessed by an ambulatory full polysomnography 2 weeks after the initiation of treatment at home. The fixed nCPAP pressure was effective (apnoea/hypopnoea and arousal indices <10 events x h(-1)) in all but two of the 10 patients studied. When the fixed nCPAP pressure was increased by 2 cmH2O in these two patients, sleep and respiration were normalized. Since only 12 ambulatory polysomnographic recordings were used to determine the effective nasal continuous positive airway pressure level, and as the device restored normal breathing and sleep in all 10 patients, it was concluded that this method of nasal continuous positive airway pressure titration may improve cost-effectiveness and reduce waiting lists in sleep laboratories.