This is the first clinical report of a case of pneumonia caused by Nocardia nova in Japan. A 52 year-old woman who had received steroids and cyclophosphamide for six years because of polymyositis was admitted to our hospital for further examination. On admission she had a mild cough, and her chest radiography and computed tomography revealed bilateral multiple nodules, some of which were cavitated. She developed a cough productive of yellow sputum and fever up to 38 degrees C. Examination of the sputum revealed a gram-positive branched organism and sputum cultures repeatedly grew Nocardia species. The isolate was identified as Nocardia nova later. Clinical recovery was obtained readily upon treatment with imipenem and trimethoprim methoxazole, though the latter drug was discontinued because of nausea and anorexia. This drug was therefore replaced with oral minocycline, which proved to be ineffective clinically although susceptibility testing of the drug showed positive sensitivity. Minocycline was replaced with clarithromycin, after which chest radiography and computed tomography showed almost total resolution of the infiltrates. Clarithromycin may be an alternative oral agent to sulfonamides or minocycline when these agents are ineffective or not tolerated.