Although pulmonary artery disease in Takayasu's arteritis has been described since 1940, it has received little attention. The clinical, hemodynamic, and angiographic features of the pulmonary involvement were studied in 22 patients with systemic arterial disease. Pulmonary involvement was found in 50 percent of the cases. Moderate pulmonary hypertension was a common finding (73 percent). Lesions were generally localized to the large and medium pulmonary vessels. None of the patients had pulmonary symptoms, but in 63 percent there were clinical, radiologic and electrocardiographic findings suggesting pulmonary hypertension or right heart strain. We believe that the pulmonary circulation should be routinely studied in patients with Takayasu's arteritis and that pulmonary involvement should be included in the classification of the disease.