Pulmonary lesions in 22 autopsy cases of Wegener's granulomatosis (WG) were studied clinicopathologically, with special emphasis on the relation of the lesions to systemic vasculitis, glomerular changes, and clinical manifestations. The pulmonary lesions were divided, on the basis of morphologic characteristics, into four types: 1) the fulminant type, which was characterized by diffusely distributed acute exudative and proliferative alveolitis with prominent small vessel vasculitis (three cases); 2) the granulomatous type, the classic granulomatous lesion (seven cases); 3) the fibrous scar type (five cases); and 4) the mixed type, which had features of both acute exudative and scar-type lesions (seven cases). Clinically, lesions of the fulminant type had rapidly deteriorating courses, terminating in respiratory failure immediately following the onset of the pulmonary manifestations, whereas those of the fibrous scar type had protracted courses. The systemic vasculitis and glomerular lesions in the cases of the fulminant type were almost exclusively fresh lesions. In contrast, the systemic lesions in the cases of the fibrous scar type were nearly always cicatricial. Thus, the morphologic features of the systemic lesions and the clinical profile in each case were well correlated with the pathologic classification of the pulmonary lesions. This correlation may support the assumption that the respiratory tract lesion plays an important role in the progression of systemic involvement in the disease. A comparative study of vascular lesions in various organs revealed some histologic differences between vasculitis in the lungs and that observed outside the respiratory tract; pathogenetic heterogeneity was thus suggested between lesions in the two locations.