Extracorporeal membrane oxygenation (ECMO) has been used for nearly 40 years for treating life threatening respiratory failure. Two historic randomized trials in adults, conducted using outdated techniques, did not show a survival advantage. However, recent case series and a large randomized controlled trial have demonstrated good outcomes from ECMO in adults. The CESAR trial, a large, multicenter, randomized trial comparing consideration for ECMO versus conventional therapy for treating severe acute respiratory failure in adults, has recently been published. The results and implications of this controversial trial are analyzed here, and a discussion of the problems inherent in assessing complex interventions in critically ill patients is provided. Additionally, the outcomes from ECMO from pandemic H1N1 influenza in Australia and New Zealand during the winter of 2009 are reviewed. Despite the inherent limitations of the methodology of the CESAR trial, the results support the use of ECMO in appropriately selected patients with life threatening acute respiratory failure. Treatments such as ECMO are extremely difficult to assess by randomized controlled trials. Observational data demonstrate excellent results from ECMO for treating patients with life threatening respiratory failure caused by pandemic H1N1 influenza, and have greatly influenced practice in Australia and New Zealand. Used as part of a multi-modal approach to treating acute respiratory failure in adults, ECMO is an important, potentially life saving, technique.