The study is designed to determine whether SCH 530348, when added to the existing standard of care for preventing heart attack and stroke (eg, aspirin, clopidogrel) in patients with a known history of atherosclerosis, will yield additional benefit over the existing standard of care without SCH 530348 in preventing heart attack and stroke.The study is also designed to assess risk of bleeding with SCH 530348 added to the standard of care versus the standard of care alone.