Over 13 years, we have seen 16 cases of proven invasive aspergillosis in 446 bone marrow transplant recipients, an incidence of 3.6%. The incidence of infection is low in patients with uncomplicated allogeneic or autologous bone-marrow transplants (< 2% and 0, respectively). Of the 16 episodes following transplantation, 10 occurred in patients with late transplant complications who were no longer in protective isolation. In patients who had focal pulmonary lesions (as diagnosed by computed tomographic scanning), culture of bronchoalveolar lavage (BAL) fluid was not an effective diagnostic procedure. In diffuse pulmonary disease due to Aspergillus, culture of BAL fluid had a sensitivity of 100%. Aspergillus species were isolated from an additional six patients who had no evidence of invasive aspergillosis. Graft rejection was a significant predisposing factor for the development of invasive aspergillosis (P < .001, log-rank test), and in our hospital, these patients now receive intravenous amphotericin B as prophylaxis. None of the six patients whose chest roentgenograms showed abnormalities before transplantation and who underwent surgical resection as part of the treatment for invasive aspergillosis developed recurrent infection.