A 66-year-old woman was given 100 mg/day of itraconazole for eight months to treat pulmonary aspergillosis with an aspergilloma. The amount of purulent sputum decreased, but open drainage was done because the fever continued and because no improvement was seen on the chest X-ray film. No aspergillus was cultured from the surgical specimen, but fungi were observed microscopically. The concentration of itraconazole in plasma was 249 ng/ml. The concentrations in specimens of the lung and of the aspergilloma obtained by thoracotomy were 81 ng/g and 837 ng/g, respectively. The high concentration in the aspergilloma had made the fungus inactive. The itraconazole concentration may have been very high for three reasons: (1) the concentration increased in purulent fluid, (2) itraconazole easily entered the aspergilloma through the root at the cavity wall, and (3) itraconazole dissolved in lipid derived from destroyed fungus.