Among the new transluminal vascular interventions currently being explored, directional atherectomy is unique in that it improves vessel patency by resecting intact portions of atherosclerotic plaque. Experimental atherectomy studies show that strips of plaque are cut away, leaving behind confluent defects within the stenotic lesions. Histologic examination of tissues excised during clinical peripheral atherectomy documents the heterogeneous morphology of peripheral atherosclerosis and shows that intimal hyperplasia is the most common cause of restenosis after therapeutic vascular interventions.