Vascular surgery is a constantly evolving specialty, and evidence-based care is a rapidly moving target. Treatment of vascular disease has changed dramatically over the 24 years since the North American Symptomatic Carotid Endarterectomy Trial (NASCET), the earliest clinical trial referenced in this chapter, was published. Although new medications, procedures, and strategies have greatly expanded the number of treatment options available to vascular surgeons and their patients, they also create challenges in generalizing prospective trial results and applying them to individual patients.