Infections are the primary cause of complications and death in patients with acute myelogenous leukemia. Current aggressive treatment protocols have improved patient survival but produce extended periods of profound neutropenia during which the patients are particularly susceptible to opportunistic infections. Candida and Aspergillus species are the most common of the fungi causing invasive infections in these patients. In a group of 77 previously untreated children with acute myelogenous leukemia begun on treatment from March 1976 to June 1984, four patients developed localized fungal infections of the lung. These initially appeared as pulmonary infiltrates on chest roentgenograms during periods of severe neutropenia (three during remission induction and one after intensive consolidation therapy). Endobronchial cultures failed to identify the infectious organism in all cases. Computerized axial tomography best defined the cavitary nature of the lesions in 2 patients. All four patients underwent surgical resection, both to establish a diagnosis (three patients) and as part of therapy. There was no operative morbidity. The organisms involved were Aspergillus (2), Torulopsis (1), and Penicillium (1). Three patients were cured of their fungal infections. The fourth patient failed to enter remission and died of a cerebral fungal abscess that developed shortly after thoracotomy. We report these cases to encourage early surgical intervention in leukemics with a localized pulmonary process consistent with a fungal infection. Resection of the primary focus obviates the risk of life threatening pulmonary hemorrhage or dissemination of the fungus and allows for early reinstitution of chemotherapy which is vital to these patients' survival.