Wegener's granulomatosis is a systemic vasculitis of medium and small arteries, venules, arterioles, and occasionally larger arteries. Classic Wegener's involves a characteristic triad of the upper respiratory tract, lower respiratory tract, and kidney involvement. The limited form of Wegener's only involves the upper and lower respiratory tracts. The etiology remains unknown, but growing evidence suggests an immunologic reaction to a specific antigen is involved. Common presenting symptoms include persistent rhinorrhea, epistaxis, oral/nasal ulcers, sinusitis, arthalgias, fever, and cough. Patients with Wegener's and alveolar hemorrhage may present with dyspnea, hemoptysis, hypoxemia, and anemia.Characteristic chest radiographic findings include single or multiple pulmonary nodules, ranging from 3 mm to 10 cm in diameter, and focal opacities, often involving localized areas of consolidation. Both nodules and areas of consolidation may cavitate. Cavities appear as unilocular or multilocular lesions with typically irregular outer wall margins. Cavities with air-fluid levels possibly indicate secondary infection, most commonly with Staphylococcus aureus or anaerobic bacteria. Less common radiographic findings include pleural effusions, bilateral diffuse infiltrates, hilar adenopathy, spontaneous pneumothorax secondary to subpleural cavitary nodule rupture, or aspergilloma in a cavity.In 1990, the American College of Rheumatology outlined the following four clinical criteria for the diagnosis of Wegener's granulomatosis: nasal or oral inflammation (bloody discharge or ulcers); abnormal chest radiograph showing nodules, fixed infiltrates, or cavities; abnormal urinary sediment (microscopic hematuria or red cell casts); and granulomatous inflammation on biopsy of an artery or perivascular area. The gold standard for diagnosis is the pathologic finding of necrotizing granulomatous vasculitis, particularly by open lung biopsy.