A 73-year-old male was admitted to our hospital because of productive cough and infiltrate on the chest roentogenogram. The underlying diseases was found to be multiple myeloma. He received a physical examination in June, 1996. The chest X-ray and CT scan on admission showed an infiltrative shadow with multiple bulla in the left upper lung field. Internal use of antibiotics and drip infusion of IPM/CS were ineffective. The chest X-ray showed air-fluid level in left upper peripheral bullous lesion and a percutaneus needle aspiration of the lung was performed. The specimen was pus with blood and microscopical examination of smears revealed no acid-fast bacilli, but Mycobacterium szulgai was isolated and identified by DNA-DNA hybridization method. The patient was treated with isoniazid and rifampicin, and improved in a few months. There are a few case reports of pulmonary infection due to M. szulgai associated with emphysematous bulla of the lung in Japan. M. szulgai infection of the lung is similar to M. kansasii infection in respect to clinical features (improvement of chest abnormal shadow, efficacy of drug).