Eight patients had lobar pneumonia caused by Aspergillus fumigatus . Dense lobar consolidation suggested a pneumonitis caused by specific bacterial agents. Hemorrhagic, necrotizing lobar pneumonia was characteristic of this type of aspergillosis, and 6 (75%) of the patients had pulmonary vascular invasion with resultant thrombosis, infarction, and hemorrhage. Clinical symptoms were consistent with pathological findings, and pleuritic chest pain, cough, dyspnea, and hemoptysis often mimicked pulmonary embolism. Factors predisposing to fungal pneumonias are felt to be hematopoietic malignancy, leukopenia, chemotherapy, and therapy with antibiotics and corticosteroids.