This study will determine the dose of Retavase that can safely be combined with ReoPro in treating acute ischemic stroke (stroke resulting from a blood clot in the brain). ReoPro and Retavase are currently approved by the Food and Drug Administration to treat heart problems caused by blockage of heart arteries. The only therapy approved by the Food and Drug Administration to treat ischemic stroke is the clot buster drug rt-PA. This treatment is effective only if begun within 3 hours of onset of the stroke, however, and most patients do not get to the hospital early enough to benefit from it.