Inclusion Criteria:

• Ischemic stroke symptoms with onset ≤ 3 hours.
• Males and females ages 18-25 years of age.
• A clot causing complete or partial occlusion via TCD in any one of the following areas: distal ICA, MCA, PCA distal vertebral or basilar occlusions. TCD must be abnormal prior to the start of Argatroban.
• Females of childbearing potential must have a negative serum pregnancy test prior to the administration of trial medication.
• Signed written informed consent by the patient or the patient's legal representative and/or guardian.
• Meet criteria for rt-PA therapy.

Exclusion Criteria:

• Evidence of intracranial hemorrhage on baseline CT scan or non-vascular cause of neurologic deficit.
• NIHSS Level of Consciousness score ≥2.
• Baseline NIHSS ≤ 5 or patient with rapidly resolving deficit or rapidly improving symptoms consistent with TPA.
• Baseline NIHSS ≥15 for right hemisphere strokes and ≥20 for left hemisphere strokes.
• Pre-existing disability with mRS ≥ 2.
• CT scan findings of hypoattenuation of the x-ray signal involving at least 2 lobes of the brain an at least 1/2 of the MCA territory.
• Absent temporal windows on TCD.
• Any evidence of clinically significant bleeding, or known coagulopathy.
• Patients currently on warfarin, with an elevated INR ≥ 1.5.
• Patients currently or within previous 48 hrs. on heparin with an elevated aPTT greater than the upper limit of normal.
• Heparin flush required for an IV line. Line flushes with saline only.
• History of ICH or significant bleeding episode within the 3 months before study enrollment.
• Major surgery or serious trauma within the last 6 weeks.
• Patients who have had an arterial puncture at a non-compressible site, biopsy of parenchymal organ, or lumbar puncture within the last 2 weeks.
• Previous stroke, myocardial infarction, post myocardial infarction pericarditis, intracranial surgery, or significant head trauma within 3months of baseline.
• Uncontrolled hypertension.
• Alcohol and/or substance abuse that would increase the risk of hemorrhage in the opinion of the investigator.
• Surgical intervention anticipated within the next 7 days.
• Hepatic dysfunction, defined by liver function tests greater than 3 times upper limit of normal at baseline, specifically SGOT and SGPT.
• Abnormal blood glucose
• History of primary or metastatic brain tumor.
• Severe mental deficit prior to onset of stroke such as organic brain disorder, schizophrenia, etc.
• Current platelet count< 100,000/mm3
• Life expectancy <3 months in the opinion of the investigator.
• Need for concomitant use of anticoagulants other than Argatroban, including any form of heparin, UFH, LMWH, defibrinogenating agent, dextran, other direct thrombin inhibitors or thrombolytic agents, GPIIb/IIIa or warfarin.
• Currently participating or has participated in any investigational drug or device study within 30 days before the first dose of study medication.
• Known hypersensitivity to Argatroban or its agents