OBJECTIVE Noninvasive ventilation is increasingly applied to prevent or treat acute respiratory failure, but its benefit on survival is still controversial for many indications. We performed a metaanalysis of randomized controlled trials focused on the effect of noninvasive ventilation on mortality. DATA SOURCES BioMedCentral, PubMed, Embase, and the Cochrane Central Register of clinical trials (updated December 31, 2013) were searched. STUDY SELECTION We included all the randomized controlled trials published in the last 20 years performed in adults, reporting mortality, comparing noninvasive ventilation to any other treatment for prevention or treatment of acute respiratory failure or as a tool allowing an earlier extubation. Studies with unclear methodology, comparing two noninvasive ventilation modalities, or in palliative settings were excluded. DATA EXTRACTION We extracted data on mortality, study design, population, clinical setting, comparator, and follow-up duration. DATA SYNTHESIS Seventy-eight studies were analyzed. Noninvasive ventilation was associated with a reduction in mortality (12.6% in the noninvasive ventilation group vs 17.8% in the control arm; risk ratio=0.73 [0.66-0.81]; p