Selenium is a trace element essential to human health.Selenium protection against cellular damage by oxygen radicals is accomplished through selenoproteins. Ischemic stroke is associated with the generation of oxygen free radicals resulting in a condition of oxidative stress. Supplementing stroke patients with antioxidant nutrients may improve survival.

Inclusion Criteria:

1. Accepted ischemic stroke by brain CT or MRI during last 72 h
2. Ischemic stroke in Middle Cerebral Artery territory
3. Volume of stroke at list one third of MCA territory
4. written informed consent.

Exclusion Criteria:

1. Known allergy to selenium
2. Severe renal failure( cr clearance under 50 ml/min or serum cr upper than 2
3. Severe hepatic failure( total bill upper than 2 or ALT/AST 5 time upper than normal limit)
4. Severe neurodegenerative disease such as severe dementia, alzheimer and Parkinson
5. Pregnancy or lactation