To evaluate the usefulness of bronchial lavage for the diagnosis of pulmonary disease due to Mycobacterium avium-intracellulare complex (MAC) infection, we examined the clinical records and bacteriologic findings of patients admitted to our hospital between 1999 and 2002 who fulfilled the 1997 American Thoracic Society (ATS) criteria for MAC pulmonary infection. Bronchoscopic examinations were performed in those patients with MAC pulmonary disease who showed negative sputum smears for mycobacteria on 3 consecutive days ( n = 14) or who could not expectorate sputum ( n = 2). The bronchial lavage sample was smear-positive for acid-fast bacilli in 8 of the 16 patients (50.0%), polymerase chain reaction (PCR)-positive for MAC in 10 of 15 (66.7%), and culture-positive for MAC in 15 of 16 (93.7%). The brushing sample was positive for MAC in 5 of 14 patients (35.7%), and transbronchial lung biopsy (TBLB)-positive for MAC in 2 of 5 (40.0%). MAC was isolated by culture of bronchial lavage samples in a higher percentage of patients than that in whom MAC was isolated by sputum culture, and we could make an early diagnosis of MAC pulmonary disease based on the smear and PCR results for bronchial lavage samples. Bronchial lavage is useful to screen sputum smear-negative patients suspected of having MAC pulmonary disease.