 This multi-center study will recruit 3000 participants 20 percent of whom will be Hispanic to find out if using aspirin and clopidogrel is more effective than using aspirin alone to prevent recurrent stroke in patients with lacunar stroke confirmed by MRI, and if lowering a patients blood pressure below the usual limits will also help prevent recurrent stroke and maintain thinking ability. Both aspirin and clopidogrel are widely-used for blood clotting and stroke prevention. Investigators intend to find out if using the drugs together is more effective than using aspirin alone. 