In a 75-year-old patient presenting with a solitary pulmonary mass, a localized form of Wegener's granulomatosis was diagnosed after lobectomy. In the absence of extrapulmonary manifestations and after a benign postoperative course, the patients was discharged without medical treatment. Three months later, diffuse alveolar hemorrhage developed abruptly, necessitating mechanical ventilation, and was followed by cardiac complications and a fatal outcome. This case and another previously reported strongly suggest the need for medical treatment in patients with a localized form of pulmonary Wegener's granulomatosis, even when complete remission after surgical resection of the lung lesion seems to have been achieved.