Transfusion-related acute lung injury is a life-threatening complication of hemotherapy associated with the transfusion of plasma-containing blood products. It is characterized by acute respiratory distress, pulmonary edema and hypoxemia. Although its frequency is unknown, Food and Drug Administration data suggest that it is the third most common cause of transfusion-associated deaths, representing 9% of reported cases. Males and females of all ages are at equal risk. To date, there is no recognized profile of individuals who are at increased risk for this complication. Although there are two purported mechanisms of injury, the preponderance of evidence suggests that passively transfused complement-activating antibodies (either granulocyte or HLA-specific) act as mediators, which result in granulocyte aggregation, activation, and microvascular pulmonary injury. With appropriate respiratory intervention, most patients recover within 96 hours of the original insult and without permanent pulmonary sequelae.