Twenty patients with Takayasu's arteritis were followed prospectively for an average of 4.6 years. Sixteen patients with active inflammatory Takayasu's arteritis were treated with glucocorticosteroids; eight responded to therapy. Six patients had clinical or angiographic progression of their vasculitis on daily corticosteroid therapy. These patients were then given cyclophosphamide together with prednisone on alternate days. Four of these 6 patients had no progression of vascular lesions while receiving cyclophosphamide; two had progression of vascular lesions after 30 and 48 months of therapy. Vascular reconstructive surgery was successful in 7 patients who tolerated a total of 13 vascular surgical procedures without major complications. One bypass graft occluded after 13 months and was revised. With corticosteroid therapy, cytotoxic therapy, and surgery, no deaths due to Takayasu's arteritis or its treatment have occurred.