Twenty-seven surgical patients who developed post-extubation hypoxemia unresponsive to routine respiratory therapy (incentive spirometry and chest physical therapy) received continuous positive airway pressure (CPAP) delivered through a mask at an inspired oxygen fraction (FIO2) of 0.45. All patients responded with an increased PaO2 and achieved a PaO2/FIO2 ratio of at least 300 with a mean CPAP of 8.3 ± 2.8 cm H2O. Mean duration of treatment was 23 ± 14 h. Two (7%) patients required reintubation, one for control of excessive secretions and the other for persistent Pseudomonas pneumonia. Mask CPAP was an effective treatment for postextubation hypoxemia in this group of surgical patients.