To determine which patients are at high risk for disseminated fungal infection and should be given systemic prophylaxis, we studied the charts of 341 patients with malignant hematologic disorders who were admitted to our institution during 10 consecutive years. These patients represented 636 admissions; during these admissions, 60 invasive fungal infections occurred, with deaths in 44 cases. All patients who died of these infections either had persisting granulocytopenia and a poor prognosis for the underlying disease or suffered from chronic graft-vs.-host disease. Two of 58 patients who had no or low-level candidal colonization developed this infection (P < .001). Nine of the 10 patients with candidal infection had microbiologically proven bacteremia within the week preceding the candidal infection. After bone marrow transplantation, 8 of 10 patients with chronic graft-vs.-host disease vs. 2 of 36 without this disease (P < .001) developed fatal infection with Aspergillus species. The results of our study reveal that patients with high-level candidal colonization who were treated for microbiologically proven bacteremia and patients with chronic graft-vs.-host disease might benefit from systemic antifungal prophylaxis.