OUTCOMES: To compare the benefits of noninvasive ventilation (NIV) plus standard therapy vs. standard therapy alone in children with acute respiratory failure; assess method effectiveness in improving gas exchange and vital signs; and assess method safety. DESIGN: Prospective, randomized, controlled study. SITE: Two pediatric intensive care units in Santiago, Chile, at Clínica Santa María and Clínica Dávila, respectively. PATIENTS AND METHODS: Fifty patients with acute respiratory failure admitted to pediatric intensive care units were recruited; 25 patients were randomly allocated to noninvasive inspiratory positive airway pressure and expiratory positive airway pressure plus standard therapy (study group); the remaining 25 were given standard therapy (control group). Both groups were comparable in demographic terms. INTERVENTIONS AND MEASUREMENTS: The study group received NIV under inspiratory positive airway pressure ranging between 12 cm and 18 cm H2O and expiratory positive airway pressure between 6 cm and 12 cm H2O. Vital signs (cardiac and respiratory frequency), Po2, Pco2, pH, and Po2/Fio2 were recorded at the start and 1, 6, 12, 24, and 48 hrs into the study. RESULTS: Heart rate and respiratory rate improved significantly with NIV. Heart rate and respiratory rate were significantly lower after 1 hr of treatment compared with admission (p = 0.0009 and p = 0.004, respectively). The trend continued over time, heart rate being significantly lower than control after the first hour and heart rate after 6 hrs. With NIV, Po2/Fio2 improved significantly from the first hour. The endotracheal intubation was significantly lower (28%) in the NIV group than in the control group (60%; p = 0.045). CONCLUSIONS: NIV improves hypoxemia and the signs and symptoms of acute respiratory failure. NIV seems to afford these patients protection from endotracheal intubation.