Hematopoietic stem cell transplantation (HSCT) has emerged as a common therapeutic option for a variety of life-threatening disorders, especially hematologic malignancies. Pulmonary complications are reported in 30% to 60% of all recipients and represent a major cause of mortality. A major proportion of these complications are the direct result of infection. This article addresses early, noninfectious causes of acute lung injury in the HSCT recipient.