The authors retrospectively reviewed their experience with bilevel positive airway pressure (BiPAP) to treat respiratory insufficiency in pediatric patients over a 5-year period. After excluding patients on chronic home BiPAP and those in whom BiPAP was used to facilitate tracheal extubation (because there were no pre-BiPAP values on which to judge its efficacy), the study cohort included 45 patients (1.5 to 22 years) in whom BiPAP was used for acute respiratory insufficiency. The primary indication for BiPAP was a primary pulmonary parenchymal process in 29 patients and postoperative atelectasis with respiratory insufficiency following cardiac or upper abdominal surgery in 16 patients. There were no differences in the pre-BiPAP values of oxygen requirement, PCO2, oxygen saturation, and respiratory rate between the 2 groups. With the application of BiPAP in patients with primary pulmonary parenchymal disease, there was a decreased oxygen requirement, PCO2, and respiratory rate. No change in oxygen saturation was noted. In patients with postoperative respiratory insufficiency, there was an improvement in all 4 parameters. There was no difference in post-BiPAP values of oxygen requirement, respiratory rate, or PCO2 between the 2 groups. The post-BiPAP oxygen saturation was greater in patients with postoperative respiratory insufficiency (96% +/- 4%) than in patients with primary pulmonary parenchymal disease (92% +/- 6%, P = .02). Endotracheal intubation was required in 11 of 29 patients with primary pulmonary parenchymal pathology versus 1 of 16 patients with postoperative atelectasis and/or respiratory insufficiency (P = .03). The chances of requiring intubation were greater in patients < or = 6 years of age (relative risk 1.9), if the oxygen requirement did not decrease to less than 60% within the first 24 hours of BiPAP use (relative risk 3.3) and if there were any PCO2 values > or = 55 mmHg during the first 24 hours of BiPAP use (relative risk 9.8). No severe complications to BiPAP were noted. BiPAP safely and effectively improves the respiratory status of and might decrease the need for endotracheal intubation in pediatric patients with acute respiratory insufficiency of various etiologies.