Invasive mold infections (IMIs) are an important cause of morbidity and mortality in patients who are undergoing bone marrow transplantation (BMT). To examine the epidemiology, risk factors, and outcome of IMIs in allogeneic BMT recipients, all cases of mold infection among 94 adult patients who underwent allogeneic BMT at this institution from 1 January 1997 through 31 December 1998 were reviewed retrospectively. Fifteen cases of IMI were identified; infection occurred a median of 102 days after BMT. Aspergillus species was the most common cause of disease, and species other than Aspergillus fumigatus were present in 53% of patients. By multivariate analysis, the variable associated with infection risk was systemic glucocorticosteroid use. Prophylactic antifungal therapy that was targeted to high-risk patients had little effect on disease incidence. These observations suggest that early identification of high-risk patients and better approaches to prevention should be explored, to reduce incidence and severity of disease in this population. © 2001 the Infectious Diseases Society of America.