Information on lung disease due to nontuberculous mycobacteria (NTM) is lacking in Singapore. A review of the records at the Central Tuberculosis Laboratory up to the end of 1988 showed that 23 patients seen between 1976 to 1988 inclusive had cultures which were repeatedly positive for NTM. Of the 23 cases analyzed, 15 were found to have lung disease which could be attributed to NTM. There were 9 males and 6 females with a male to female ratio of 1.5:1. The patients were either middle aged or elderly. The 2 main infective agents were M avium-intracellulare and M kansasii. Ten (67%) patients had moderately advanced and 5 (33%) had far advanced disease. Concurrent disease of the lung was present in 10 patients (67%). Seven (47%) patients had bronchiectasis, 1 (7%) had both bronchiectasis and chronic obstructive pulmonary disease (COPD) and 2 (13%) had COPD. A past history of pulmonary tuberculosis was present in 10 patients (67%). Lung disease due to NTM is uncommon in Singapore. Treatment failure was attributed to poor compliance, a possibility which could not be excluded in those patients who had adverse reactions.