Autologous BMT performed in a 57-year-old woman with relapsed large cell lymphoma was complicated by two consecutive episodes of diffuse alveolar hemorrhage (DAH). The second episode occurred immediately after infusion of autologous BM. DAH is an increasingly recognized complication of autologous BMT and carries a high mortality. It is characterized by dyspnea, cough, bilateral pulmonary infiltrates and progressively bloodier aliquots of bronchoalveolar lavage fluid. The pathogenesis is probably multifactorial involving an initial insult to lung endothelium with inflammatory cells serving as the mediators of subsequent injury. The rapid development of DAH following marrow infusion strongly implicates DMSO as a potential cause in our patient.