Single center randomized clinical trial, to evaluate the safety and efficacy of carotid artery stenting using the RX ACCULINK™ Carotid Stent System with RX ACCUNET™ Embolic Protection System or PercuSurge GuardWire® 3-6 Temporary Occlusion and Aspiration System using Angiomax (bivalirudin)versus heparin as the anticoagulant for treatment of occlusive carotid artery disease in low and high risk patient cohorts.

Inclusion Criteria:

• The patient must be at least 18 years of age.
• The patient must have a significant diameter reduction of the extracranial or intracranial internal or common carotid artery, defined as ≥50% stenosis for symptomatic patients or ≥80% stenosis for asymptomatic patients determined by carotid duplex ultrasound scan and/or carotid angiography.
• Female patients with child bearing potential must have a negative pregnancy test.
• The patient and the patient's physician must agree to have the patient return for a 30-day and one-year clinical and ultrasound imaging follow-up evaluations as indicated in the protocol.
• Reference vessel diameter ≥ 3.5 mm - ≤ 9.0 mm diameter.

Exclusion Criteria:

• The patient has had a recent (<4 weeks) disabling stroke or dementia with major neurologic deficit (stroke scales: Barthel <60, NIH >15, or Rankin >3) at pre-procedure neuro exam.
• The patient has had within four weeks of the treatment procedure an intracranial hemorrhage, hemorrhage stroke, major stroke, or any stroke with mass effect demonstrated on MRI or CT.
• The patient has a known allergy to heparin, bivalirudin, aspirin or to anti-platelet agents that prevents taking aspirin plus ticlopidine or aspirin plus clopidogrel.
• The patient has received fractionated or unfractionated heparin within 8 hours prior to the procedure.
• The patient has a history of prior life-threatening radiocontrast reaction that cannot be pre-treated.
• The patient has a history of bleeding diathesis or coagulopathy within 3 months.
• The patient is currently participating in another study protocol that may influence either procedure results or follow-up evaluations.
• Plasma/serum creatinine > 3.0 mg/dl at time of intervention.
• Hemodynamic instability at the time of intervention.
• Previous stent placement in the ipsilateral carotid distribution.

Angiographic Exclusion Criteria

• The patient has an intracranial tumor, or cerebral arterio-venous malformation(s) > 5mm, aneurysms or severe intracranial stenosis distal to target lesion.
• The patient has inaccessible intracranial arterial stenosis greater in severity than the extracranial internal carotid artery lesion.
• There is angiographic evidence of significant intra-luminal thrombus burden with presumed increased risk of plaque fragmentation and consequent distal embolization.
• There is total occlusion of the ipsilateral carotid artery treatment site with TIMI 0 flow characteristics.
• The reference segment diameter (internal carotid artery segment cephalad to the lesion) is less than 3 millimeters by operator visual estimate.
• The patient has peripheral vascular, supra-aortic or internal carotid artery tortuosity precluding use of catheter-based techniques required for successful CSSA