Inclusion Criteria:  Diagnosis of ischemic stroke causing measurable neurological deficit Onset of symptoms <4.5 h before treatment begins Age ≥18 y  Exclusion Criteria:  Significant head trauma or prior stroke in the previous 3 mo Symptoms suggest SAH Arterial puncture at noncompressible site in previous 7 d History of previous intracranial hemorrhage Intracranial neoplasm, AVM, or aneurysm Recent intracranial or intraspinal surgery Elevated blood pressure (systolic >185 mm Hg or diastolic >110 mm Hg) Active internal bleeding Acute bleeding diathesis, including but not limited to Platelet count <100 000/mm3 Heparin received within 48 h resulting in abnormally elevated aPTT above the upper limit of normal Current use of anticoagulant with INR >1.7 or PT >15 s Current use of direct thrombin inhibitors or direct factor Xa inhibitors with elevated sensitive laboratory tests (eg, aPTT, INR, platelet count, ECT, TT, or appropriate factor Xa activity assays) Blood glucose concentration <50 mg/dL (2.7 mmol/L) CT demonstrates multilobar infarction (hypodensity >1/3 cerebral hemisphere) Relative exclusion criteria Recent experience suggests that under some circumstances, with careful consideration and weighting of risk to benefit, patients may receive fibrinolytic therapy despite ≥1 relative contraindications. Consider risk to benefit of intravenous rtPA administration carefully if any of these relative contraindications is present Only minor or rapidly improving stroke symptoms (clearing spontaneously) Pregnancy Seizure at onset with postictal residual neurological impairments Major surgery or serious trauma within previous 14 d Recent gastrointestinal or urinary tract hemorrhage (within previous 21 d) Recent acute myocardial infarction (within previous 3 mo)