The aim of this study was to evaluate the changes in chest CT findings examined successively in patients with Mycobacterium avium-intracellulare complex (MAC) infection. We carried out a retrospective study of 25 patients with MAC infection who had serial CT scans. Patients included 18 women and seven men with a median age of 66 years. Mean (+/- SE) follow-up interval between the first and second CT was 27.5 +/- 4.2 months. The serial chest CT scans were reviewed with consensus reading by two observers. At the first chest CT examination, we found the following: bronchiectasis (in 133 of 250 fields), cavity formation (11 of 250 fields), centrilobular nodules (167 of 250 fields), air-space disease (30 of 250 fields) and nodules (81 of 250 fields). The middle lobe and lingula were frequently involved. Centrilobular nodule scores improved in seven patients; disease progressed in nine patients and was stable in nine patients. In addition, bronchiectasis scores improved in four patients; disease progressed in 15 patients and was stable in six patients. The score of bronchiectasis in the second CT was significantly higher than in the first CT. In conclusion, our data suggest that centrilobular nodules and bronchiectasis are frequent observations in patients with MAC. In addition, progression of bronchiectasis appeared to be caused by MAC infection.