We have performed serial bronchoalveolar lavage (BAL) examination in two patients with asperigilloma and compared that of total cell count and cell population with control groups (5 non-smokers, 10 smokers) and other pulmonary infectious diseases: 7 each with mycoplasmal pneumonia and pulmonary tuberculosis, 6 with bacterial pneumonia, and 5 with chlamydial pneumonia. Miconazole (MCZ) by drip intravenous infusion of 400 mg/day and flucytosine (5-FC) by oral intake of 4.5 to 6.0 g/day were administered to one patient with aspergilloma, and we studied the serum and BALF concentration about 5 hours after administration. The followings results were obtained: 1. In aspergilloma, the cell population of neutrophils in BALF increased compared with control groups (p < 0.01) and other pulmonary infectious disease. 2. The serum and BALF levels of MCZ ranged from 0.1 to 0.3 micrograms/ml, < 0.1 14.4 micrograms/ml, respectively. On the other hand, the serum and BALF levels of 5-FC ranged from < 0.2 to 9.3 micrograms/ml, and < 0.4 to 1.5 micrograms/ml, respectively. From these results, we consider that neutrophils play the main role in the immune host defense in aspergilloma, and the combination of intracavitary infusion of MCZ and oral administration of 5-FC should be the treatment of choice.