&NA;Survival and allograft function in lung transplant recipients are limited by the development of bronchiolitis obliterans. The precise pathogenesis of bronchiolitis obliterans remains unknown. However, studies indicate that epithelial injury in the lung allograft can be induced by a variety of factors, including infections. Indeed, infection is among the most significant complications in lung transplant recipients, and some infectious agents are recognized to trigger allograft injury. Cytomegalovirus is an immunomodulating herpesvirus that causes an upregulation of human leukocyte antigen class I and intracellular adhesion molecule I in the epithelial cells of the lung allograft, resulting in activation of T helper and cytotoxic T cells. Respiratory viruses activate inflammatory mechanisms in the transplant lung that may lead to acute allograft rejection during and after respiratory viral infections. More importantly, data show the development of bronchiolitis obliterans after infection with these common pathogens. This review examines the published data implicating viruses and other infectious pathogens in the development of bronchiolitis obliterans in lung transplant recipients.