We used mask continuous positive airway pressure (CPAP) in seven patients with acute hypercapnic respiratory failure in an attempt to avoid endotracheal intubation and mechanical ventilation. Mask CPAP was started at 5 cm H2O and then increased to a maximum of 10 cm H2O depending on the clinical response. In five patients, CPAP significantly improved gas exchange; four of these patients were weaned to oxygen by face mask without needing intubation. In two patients, gas exchange deteriorated even with CPAP of 10 cm H2O. No barotrauma or adverse hemodynamic effects were associated with CPAP. We conclude that a trial of mask CPAP may be warranted before intubation of an alert, acutely hypercapnic patient with COPD.