Background : Because of the low sensitivity of sputum smear and culture, diagnosis of nontuberculous mycobacterium (NTM) pulmonary disease, especially in patients with bronchiectasis, is often difficult. We investigated the usefulness of bronchoscopy for the diagnosis of NTM pulmonary disease including M. avium complex (MAC) and M. abscessus in patients with bronchiectasis and multiple pulmonary nodules on chest computed tomography (CT). Methods : We reviewed 48 cases of patients who were performed bronchoscopic bronchoalveolar lavage (BAL) and transbronchial lung biopsy (TBLB) under suspect of NTM pulmonary disease based on CT findings of bronchiectasis and multiple nodules from April 2002 to June 2003. Results : Twenty five of the 48 patients (54%; 12 MAC, 14 M. abscessus) were diagnosed as NTM pulmonary disease on the basis of the American Thoracic Society diagnostic criteria for NTM pulmonary disease. Sixteen of the 21 patients (76%; 5 MAC, 11 M. abscessus) with 3 or more positive sputum cultures of NTM were confirmed tissue invasion by TBLB. Five of the 24 patients (21%; 4 MAC, 1 M. abscessus) who could not be diagnosed with sputum cultures were diagnosed by bronchoscopic BAL and TBLB. Conclusion : Bronchoscopy is helpful for the diagnosis of NTM pulmonary disease and confirmation of tissue invasion by NTM, not only MAC but also M. abscessus, in patients with bronchiectasis and multiple nodules on chest CT scan.