Use of the membrane oxggenator has been advocated in the management of severe respiratory insufficiency. We have compared this method to conventional therapy in an experimental model in which 23 dogs were subjected to aspiration with 0.1 N HC1 and 18 were supported with a volume respirator and positive end-expiratory pressure or placed on partial bypass using a membrane oxygenator for 12 to 24 hours. Adequate oxygenation (POX greater than 100 mm Hg) was achieved with the membrane oxygenator. The increase in lung weight during conventional therapy was significantly greater than during membrane oxygenator support. Extracorporeal support during recovery from severe pulmonary injury allows pulmonary artery pressure to be controlled and reduces the expected increase in lung water.