The efficacy and complications of bilevel positive airway pressure nasal mask ventilation for 22 patients with acute hypercapnic respiratory failure were reviewed retrospectively. The median patient age was 73 years (range, 57-92 years). The most common primary diagnosis (77%) was chronic obstructive pulmonary disease. The median duration of ventilation was 72.0 hours (range, 0.9 hours to 35 days). Within a median of 12 hours (range, 1-24 hours) after the initiation of therapy, there were significant improvements in the arterial oxygen and carbon dioxide tensions, oxygenation ratio, and arterial-alveolar ratio. Fourteen patients (64%) were treated successfully. Success with therapy was associated with a lower Acute Physiology and Chronic Health Evaluation score, a higher arterial oxygen tension, higher oxygenation and arterial-alveolar ratios, and lower respiratory and pulse rates. Complications were uncommon. We conclude that bilevel positive airway pressure nasal mask ventilation can be useful for patients with acute hypercapnic respiratory failure but who are otherwise clinically stable.