Aggrenox Prevention of Access Stenosis

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 * A new or planned arteriovenous (AV) graft placed in any location for the purpose of hemodialysis. (Any type of graft material and any configuration of the access is acceptable). * 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. * Known allergy or adverse reaction to Aggrenox or any of its study components (dipyridamole and aspirin). * Required use of warfarin, dipyridamole, non-steroidal antiinflammatory drugs or other antiplatelet agents other than aspirin. * Current uncontrolled hypertension with systolic blood pressure in excess of 200 mm Hg or diastolic blood pressure in excess of 115 mm Hg. * 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.