Clopidogrel Prevention of Early Arteriovenous (AV) Fistula Thrombosis

Fistula Study Protocol Inclusion Criteria: * Age 18-21 depending on state regulations * Life expectancy of at least six months * Chronic renal failure with anticipated start of hemodialysis within six months of enrollment, or current dialysis dependence * Planned creation of native upper extremity AV fistula * The patient is not on aspirin, or the patient is on aspirin but has not had a myocardial infarction or a cerebrovascular accident within the past 12 months. * The patient is expected to stay at a participating dialysis facility for at least 6 months. * The patient's physician(s) will allow the patient to participate. * Ability to give informed consent. Exclusion Criteria: * Women must not be pregnant, breastfeeding, or plan to be pregnant during the course of the study. * The presence of ongoing bleeding. * The presence of a known bleeding disorder (e.g., hemophilia or von Willebrand's disease). * Recent bleeding episode requiring transfusion within 12 weeks of entry. * The presence of acute ulcer disease. Acute ulcer disease is defined as a new diagnosis of peptic disease including esophagitis, gastritis, or ulcer or the initiation of treatment with proton pump inhibitors, H2 blockers or therapy for Helicobacter pylori within three months prior to obtaining consent. * A condition which prohibits discontinuation of anticoagulant drugs, aspirin, or nonsteroidal anti-inflammatory drugs during the six week study drug administration period. Use of heparin during dialysis is allowed. * Required use of oral or intravenous glucocorticoids at a dose greater than the equivalent of prednisone 15 mg per day during the six week study drug administration period. * Current unstable angina. * Required use of clopidogrel. * Known hypersensitivity to clopidogrel. * Medical considerations making anti-platelet therapy dangerous. * Current uncontrolled hypertension with systolic blood pressure in excess of 200 mm Hg or diastolic blood pressure in excess of 115 mm Hg at the time of enrollment. * Baseline platelet count less than 75,000/mm3. * Known advanced liver disease with decompensated cirrhosis, jaundice, ascites or bleeding varices. * Current problem with substance abuse. * Concurrent participation in another medical intervention trial. * Anticipated non-compliance with medical care based on physician judgment. * Patient refusal.