Abciximab is a drug that prevents platelets from sticking together and forming a clot. There are limited studies using abciximab in the treatment of strokes. This phase III, multicenter, randomized, double-blind, placebo-controlled, parallel group study is designed to assess the effectiveness and safety of abciximab for treatment of acute ischemic stroke, in helping dissolve clots in brain arteries so that blood and oxygen can flow better and there may be less brain damage.