The rate of pulmonary nontuberculous mycobacteriosis (NTM) in the total pulmonary mycobacteriosis has been continuously increasing. While M. avium complex is the most common cause of NTM, there are a few case reports of pulmonary infection due to M. szulgai. We described two cases of pulmonary NTM caused by M. szulgai. A 75-year-old male was admitted to our hospital because of dyspnea on effort, and productive cough. A chest X-ray showed an infiltrative shadow with cavity in the right upper lobe. A sputum smear for mycobacteria was positive, and a culture grew M. szulgai which was identified by DNA-DNA hybridization. He was treated with isoniazid, rifampicin, and ethambutol. His symptoms and CT and X-ray findings improved, and his sputum smear and culture converted to negative for mycobacteria. Second case was a 73-year-old male who had previously been diagnosed as MAC and pulmonary aspergillosis, and had been treated with antituberculous and antifungal drugs. He was readmitted to our hospital, because of general fatigue and hemoptysis. A chest X-ray revealed a consolidation with bronchiectasis and cavity in the both upper lung fields. A sptum smear for mycobacteria was positive, and a grown culture was identified as M. szulgai. He was treated with rifampicin, ethambutol and kanamycin based on the results of susceptibility testing. After 3 months of this treatment his sputum smear and culture converted to negative for mycobacteria, and his symptoms, and CT and X-ray findings improved.