Extracorporeal membrane oxygenation (ECMO) in a venoarterial perfusion circuit was used to provide support of gas exchange during bronchopulmonary lavage in a 32-year-old man with pulmonary alveolar proteinosis and severe arterial hypoxemia. Prior to the lavage, Pao2 during mechanical ventilation with 100% oxygen and positive end-expiratory pressure was only 125 mm Hg. Extracorporeal perfusion at a flow rate of 3 liters/min, with oxygen delivery of 244 ml/min, increased the Pao2 to 227 mmHg and lowered the mean pulmonary artery pressure from 28 to 24 mm Hg. During bronchopulmonary lavage and ECMO, the Pao2 ranged between 46 and 96 mm Hg. After the procedure, pulmonary performance decidely improved. By reducing the chances of fatal hypoxemia, ECMO allowed treatment to be instituted for this potentially reversible disorder and proved helpful as a form of support during the management of pulmonary alveolar proteinosis when severe hypoxemia may have other wise precluded bronchopulmonary lavage.