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 greater than or equal to 50% stenosis for symptomatic patients or greater than or equal to 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 must provide written informed consent using a form that is reviewed and approved by the human Investigation Review Board of the Washington Hospital Center

Exclusion Criteria:

• The patient has had a recent (<4 weeks) disabling stroke or dementia with major neurologic deficit
• 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 the time of intervention
• Hemodynamic instability at the time of intervention
• There is total occlusion of the ipsilateral carotid artery treatment site with TIMI 0 flow characteristics
• The patient has peripheral vascular, supra-aortic or internal carotid artery tortuosity precluding use of catheter-based techniques required for successful CSSA