Two cases of pulmonary disease in a 54 year-old female and a 70 year-old male patient due to Mycobacterium avium-intracellulare complex(MAIC) and a case of pulmonary infection ina 69 year-old male patient due to M. fortuitum(MF) were found recently in this institute. All three patients had a long history of anti-tuberculous chemotherapy because they were initially diagnosed as pulmonary tuberculosis. A 70 year-old male patient infected with MAIC had an unsuccessful chemotherapy history of isoniazid(INH), para-aminosalicylic acid(PAS) and streptomycin(SM) with an incomplete, temporary, symptomatic improvement, for three years since 1964 when he was first diagnosed as pulmonary tuberculosis on physical examination. A 54 year-old female patient infected with MAIC also had an unsuccessful chemotherapy history with the various anti-tuberculous drugs since 1958. Both patients discharged large number of MAIC in their sputum specimens for at least more than one year, but no M. tuberculosis at all. A 69 year-old male patient infected with MF was diagnosed as moderately advanced pulmonary tuberculsis in 1977. Combined chemotherapy with INH+PAS+pyrazinamide(PZA) improved his clinical symptoms, however, his chest radiograph was deteriorated again in 1980 one year after he stopped therapy. Therefore he started chemotherapy again with INH+ethionamide(TH)+cycloserine(CS) but no improvement was noticed. MF was cultured from his sputum in August 1981 and he continuously discharged the same bacilli until last examination of January 1982. Whether all three patients were initially !infected with nontuberculous mycobacteria or complicated with predisposing tuberculosis was not clear because there were no reliable bacteriological examination records.