This study is looking to see if niacin will lessen atherosclerotic plaque inflammation and favorably affect circulating levels of endothelial progenitor cells and microparticles in people with atherosclerotic disease on chronic statin therapy.

Inclusion Criteria:

• Men age 55 years and above with coronary artery disease or women age 65 years and above with coronary artery disease OR Men age 45 years and above with both coronary artery disease and carotid or lower extremity peripheral artery disease or women age 55 years and above with both coronary artery disease and carotid or lower extremity peripheral artery disease.
• Subjects must be on statin monotherapy, defined as a stable statin dose for at least 12 weeks, with no anticipated need for further titration during the study period

Exclusion Criteria:

• Anxiety or claustrophobia prohibiting imaging
• History of allergy to intravenous contrast, iodine, or shellfish
• Renal insufficiency
• History of allergy or severe intolerance to niacin
• History of diabetes mellitus or elevated fasting glucose
• Moderate to severe gout
• Peptic ulcer disease
• Acute coronary syndrome, transient ischemic attack or cerebrovascular accident, or acute limb ischemia in the preceding 12 months
• Heart failure or unstable angina pectoris
• Use of daily non-statin lipid-altering therapy prior to the initiation of study medication

12 weeks