Six cases of pulmonary nocardiosis are reported. All patients were compromised hosts treated with corticosteroids and/or immunosuppressive agents. The clinical presentations ranged from malaise to respiratory failure. The radiological manifestations varied from a solitary nodule to extensive cavitary bronchopneumonia with distant dissemination. The diagnosis was made by sputum culture in one, open lung biopsy in 3, and at autopsy in 2 others. In 3 patients, in whom early diagnosis was made, the infection was controlled by sulfonamide therapy.