The early clinical trials and the more recent CAS registry studies have led to greater operator experience and significant improvements in CAS technique. One of the fundamental advances in CAS technique has been the development of EPDs during the past several years. Although no randomized trials have compared CAS with and without EPDs, and there are still those who are not convinced of their efficacy in reducing procedure-related particle emboli and strokes, best available data suggest that EPDs reduce the risk of stroke, and their use has become standard practice in CAS.31,32 The 3 approaches used to achieve distal embolic protection are (1) distal balloon occlusion, (2) distal filter placement, and (3) proximal occlusion with flow reversal (Figure 1). Distal balloon occlusion systems are flexible, low-profile systems capable of negotiating rather tortuous vessels and high-grade stenoses. Although these systems generally provide complete capture of released particulate debris, the main disadvantage is the required period of intracerebral flow arrest during balloon angioplasty and stent deployment. The most commonly used EPDs are distal filter devices, and there are 4 devices approved in the United States: AccuNet (Abbott Vascular, Redwood City, California), Spider (ev3, Plymouth, Minnesota), Emboshield (Abbott Vascular), and Angioguard (Cordis, Warren, New Jersey). The main advantage of the distal filter device is the preservation of antegrade cerebral flow throughout the procedure while providing capture of released embolic particulate debris (Figure 2). However, filter systems tend to be bulkier and more rigid than other classes of EPDs. Flow reversal EPDs, originally described by Parodi et al,33 are based on the same surgical principle used to measure carotid stump pressures during CEA, whereby in the presence of patent intracranial circulation, proximal occlusion of the common carotid artery and the external carotid artery causes reversal of flow in the internal carotid artery. The obvious advantage of flow reversal EPDs is the ability to gain cerebral embolic protection before crossing the lesion with bulky wires and catheters.