A 75-year-old man was admitted with cough, purulent sputum, fatigue and weight loss of 10 kg of some months’ duration. His chest radiograph showed poorly defined opacities in the right lung. Eleven years before admission an epidermoid carcinoma of the right lung had been diagnosed and a right bilobar resection had been performed. The patient remained asymptomatic for 8 years. Cultures of 4 consecutive sputum samples were positive for mycobacteria that were identified as <i>Mycobacterium szulgai</i> by gas chromatography. A 6-month regimen of rifampin, isoniazid and pyrazinamide resulted in complete eradication of the mycobacterium. <i>M. szulgai</i> is an unusual pathogen in humans. In the English literature, only 35 cases of pulmonary disease have been reported. Its clinical and radiological characteristics are similar to tuberculosis but in contrast to the rest of the non-tuberculous mycobacteria, <i>M. szulgai</i> has shown in vitro and in vivo susceptibility to most primary antituberculosis drugs.