The rising incidence of pulmonary aspergillosis is a major clinical concern. However, only a limited number of antifungal drugs are available in Japan that are effective for pulmonary Aspergillus infections. Micafungin (MCFG), a newly developed echinocandin family antifungal drug, has potent antifungal activity in vitro, but few reports detailing its clinical effectiveness have been published to date. A retrospective study was performed using data from nine patients (seven males and two females) with chronic invasive forms of pulmonary aspergillosis, who were treated with either MCFG alone or together with other antifungal drugs between April 2003 and March 2004. The overall efficacy of the treatments was evaluated in the terms of clinical, mycological, serological and radiological responses. The average age of the patients was 61.9 (20-83) years old. Four patients received only MCFG and the remaining five patients were treated with MCFG in combination with amphotericin B (AMB) only (1 patient), itraconazole (ITC) only (2 patients) or AMB backed up by ITC during AMB discontinuation periods (2 patients). The mean duration of MCFG administration was 59.2 (28-96) days. Overall, the treatment was judged to have been effective for seven of nine patients. No patient's condition deteriorated in response to treatment. Administration of MCFG alone was judged to have been effective in three of four patients. No notable adverse effects were documented during MCFG administration. These data suggest that MCFG may be an effective and safe antifungal drug for the treatment of chronic invasive forms of pulmonary aspergillosis.