Ischemic stroke during or following cardiac catheterization may be secondary to diverses mechanisms. Formation and detachment of clots in the catheter wall and embolization of a breaked atheromatous lesion are most frequently. The visualization of clots free in the interior of bypass aortocoronary graft is extremely rare and poorly documented. With angiographic evidence we present a case of cerebral acute ischemia secondary to migration of an embolus from a saphenous vein aortocoronary bypass graft. This case shows a different mechanism of cerebral ischemia.