Background: Non-invasive positive pressure ventilation (NIPPV), using continuous positive airway pressure (CPAP) or bilevel ventilation, has been shown to reduce the need for invasive mechanical ventilation in patients with acute cardiogenic pulmonary oedema. We assessed additional benefits of NIPPV in a meta-analysis. Methods: Meta-analysis comparison in acute cardiogenic pulmonary oedema was undertaken to compare (1) CPAP with standard therapy (oxygen by face-mask, diuretics, nitrates, and other supportive care), (2) bilevel ventilation with standard therapy, and (3) bilevel ventilation with CPAP, incorporating randomised controlled trials identified by electronic and hand search (1966-May, 2005). In 23 trials that fulfilled inclusion criteria, we assessed the effect of NIPPV on hospital mortality and mechanical ventilation, estimated as relative risks. Findings: CPAP was associated with a significantly lower mortality rate than standard therapy (relative risk 0·59, 95% CI 0·38-0·90, p=0·015). A non-significant trend towards reduced mortality was seen in the comparison between bilevel ventilation and standard therapy (0·63, 0·37-1·10, p=0·11). We recorded no substantial difference in mortality risk between bilevel ventilation and CPAP (p=0·38). The need for mechanical ventilation was reduced with CPAP (0·44, 0·29-0·66, p=0·0003) and with bilevel ventilation (0·50, 0·27-0·90, p=0·02), compared with standard therapy; but no significant difference was seen between CPAP and bilevel ventilation (p=0·86). Weak evidence of an increase in the incidence of new myocardial infarction with bilevel ventilation versus CPAP was recorded (1·49, 0·92-2·42, p=0·11). Heterogeneity of treatment effects was not evident for mortality or mechanical ventilation across patients' groups. Interpretation: In patients with acute cardiogenic pulmonary oedema, CPAP and bilevel ventilation reduces the need for subsequent mechanical ventilation. Compared with standard therapy, CPAP reduces mortality; our results also suggest a trend towards reduced mortality after bilevel NIPPV.