Atherosclerosis is a disease in which the blood vessels become blocked by plaques (consisting of fat, calcification, and fibrous tissue), reducing blood flow to vital organs and tissues.Blockage of the carotid arteries in the neck is a major cause of stroke. One way of treating carotid atherosclerosis is with cholesterol-lowering drugs called statins. Statins have been shown to reduce the risk of coronary heart disease by 24-40% and risk pf stroke by 11-30%.The purpose of this study is to determine if short term treatment with atorvastatin causes early favorable changes in the plaques that block blood flow through the carotid arteries. These changes can be assessed 1) by taking pictures of the carotid arteries with MRI and Ultrasound before and after statin treatment, and 2) by special studies of the plaques removed from the carotid arteries by surgery.