The complications of endotracheal intubation are particularly frequent in patients with obstructive sleep apnoea syndrome (OSAS). We prospectively tested nasal ventilation in such patients admitted for acute respiratory failure. Six consecutive patients, aged 17-70 yrs, were selected for the study. All patients were confused or severely obtunded, Glasgow Coma Score (GCS) 10 (SD 2). With nasal bi-level positive airways pressure (BiPAP) all these patients improved clinical status and arterial blood gas values, avoiding intubation and invasive mechanical ventilation. The median pH increased from 7.26 (SD 0.06) to 7.36 (0.01) and to 7.43 (0.02) after, 1-3 and 24 h of nasal ventilation, respectively. Nasal ventilation lasted an average of 21 (3) h on the first day. All patients were discharged home after a median hospital stay of 28 (11) days.