Inclusion Criteria1. Men and non-pregnant women over age 18 who have had an acute ischemic stroke referable to the anterior circulation, as diagnosed by one of more of the following: clinical judgment, head CT, and/or MR imaging [i.e. a positive diffusion-weighted imaging (DWI) abnormality].
2. Clinical syndrome not likely to represent transient ischemic attack (TIA) or other non-stroke etiology
3. Patient must be neurologically stable at the time of first MRI scan (i.e. stable NIH Stroke Scale score).
4. Initial MRI scan obtainable within 48 hours of symptom onset.
5. A pre-existing diagnosis of hypertension, either treated or untreated.
6. Average of two mean arterial blood pressures (separated by at least five minutes) at time of enrollment.
Exclusion Criteria1. Patients who have taken an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) within seven (7) days of admission.
2. Patients who received intravenous or intra-arterial r-TPA for their current symptoms, or those who underwent mechanical thrombolysis.
3. Patients with hemorrhagic strokes, as seen on the initial head CT.
4. Patients with stroke-like symptoms, but no demonstrable lesion on DWI, or a DWI lesion < 2 cm in diameter (greatest dimension).
5. Patients with high-grade (>70%) internal carotid artery stenosis or occlusion ipsilateral to the current stroke.
6. Patients with high-grade aortic or mitral stenosis.
7. Patients with a previous adverse reaction to valsartan or other ARBs.
8. Patients with contraindications for MRI, including pacemakers, claustrophobia, or severe obesity.
9. Patients who are medically unstable for MR imaging, as determined by the treating team.
10. Patients with a severe co-existing disease that may interfere with the conduct of the study.
11. Patients receiving investigational drug therapies.
12. Informed consent cannot be obtained from the patient or an appropriate surrogate.