The non-relapse mortality of autologous stem cell transplant is low enough that the procedure has been extended to older patients with non-Hodgkin's lymphoma. We treated 537 non-Hodgkin's lymphoma patients with high-dose chemotherapy consisting of busulfan, cyclophosphamide, and etoposide followed by autologous stem cell transplant. Sixteen patients were identified who died of pulmonary complications at a five-year incidence of 3.6%. Risk factors for pulmonary mortality included older age and lower baseline D(CO) and FEV1. We conclude that high-dose busulfan is associated with pulmonary mortality after autologous transplant, particularly in older patients.