CAPITAL: Carotid Artery Plaque Intravascular Ultrasound Evaluation

Inclusion Criteria: * \>18 years of age * Patient must be: Symptomatic with lesions \>/= to 50% stenosis, or Asymptomatic with lesions of \>/= to 75% stenosis in at least one carotid artery, specific to the internal carotid artery, common carotid artery or bifurcated region; documented through acceptable ultrasound studies, completed within 30 days of recruitment. * For patients with bilateral carotid disease- procedures need to be staged greater than 30 days apart. The lesion that has a greater degree of stenosis will be considered as the index procedure. * Women of childbearing potential must have a negative pregnancy test within 7 days prior to treatment. * The patient is able to give informed consent. Exclusion Criteria: * The patient is experiencing a new (acute) neurologic event or has experienced a stroke within the last 30 days prior to enrollment. * The patient has intracranial tumors, arterial vascular malformations \>5mm, aneurysms or severe intracranial stenosis distal to the target lesion. * Presence of thrombus at the target site or loose 'floating' debris as determined by duplex analysis and/or angiography. * Existing hemorrhagic disease or coagulation problems creating inability to obtain homeostasis at entry site. * The patient has an allergy to, or is unable to tolerate, heparin, concomitant medications (clopidogrel or ticlid, aspirin) or to nitinol metal. * The patient has a history of or known reaction to radiocontrast agent (radiopaque dye) and is unable to be premedicated. * Coumadin treatment that has continued during the 48 hours prior to enrollment and an INR above hospital normals (i.e. in the event of atrial fibrillation or prosthetic valve replacement). * Hemodynamic instability at the time of intervention. * Severe chronic renal insufficiency (plasma/ serum creatinine\> 2.5 mg/dL) at the time of intervention, except in patients on dialysis.