This investigation evaluates, in a prospective, randomized and controlled manner, whether noninvasive ventilatory support (NIVS) with bilevel positive airway pressure (BiPAP) facilitates recovery from acute respiratory failure (ARF) in patients with chronic obstructive pulmonary disease (COPD). Twenty four patients (mean age (+/-SEM) 68 +/- 2 yrs) with COPD (forced expiratory volume in one second (FEV1) at discharge 33 +/- 2% predicted), who attended the emergency room because of ARF (pH 7.33 +/- 0.01; arterial oxygen tension (Pa,O2) 6.0 +/- 0.2 kPa; arterial carbon dioxide tension (Pa,CO2) 7.9 +/- 0.3 kPa), were initially randomized. Four out of the 14 patients (29%) allocated to received NIVS did not tolerate it. Of the remaining 20 patients, 10 received NIVS with BiPAP in a conventional hospital ward during the first 3 days of hospitalization (two daytime sessions of 3 h duration each). All 20 subjects were treated with oxygen, bronchodilators and steroids. On the first and third hospitalization days, before and 30 min after withdrawing oxygen therapy and/or BiPAP ventilatory support, we measured peak expiratory flow, arterial blood gas values, ventilatory pattern, occlusion pressure (P0.1), and maximal inspiratory (MIP) and maximal expiratory (MEP) pressures. All patients were discharged without requiring tracheal intubation and mechanical ventilation. Hospitalization time was similar in both groups (11.3 +/- 1.3 vs 10.6 +/- 0.9 days, control vs BiPAP, respectively). Arterial oxygenation, respiratory acidosis and airflow obstruction improved significantly throughout hospitalization in both groups. By contrast, the ventilatory pattern, P0.1, MIP and MEP did not change. NIVS with BiPAP did not cause any significant difference between groups. We conclude that noninvasive ventilatory support with bilevel positive airway pressure does not facilitate recovery from acute respiratory failure in patients with chronic obstructive pulmonary disease. Furthermore, a substantial proportion of patients (29%) do not tolerate noninvasive ventilatory support under these circumstances. From these results, we cannot recommend the use of noninvasive ventilatory support with bilevel positive airway pressure in the routine management of chronic obstructive pulmonary disease patients recovering from acute respiratory failure.