Acute ischemic stroke, a major subtype of acute stroke is one of the leading cause of death and disability throughout the world. At present, the diagnosis of acute ischemic stroke is mainly based on Computer Tomography or Magnetic Resonance Imaging. This article is a critical and descriptive review on S100β protein as a biomarker in acute ischemic stroke. We searched Pubmed database with key words or terms such as "S100β protein", ‘Acute ischemic stroke’ and the articles were analyzed for the results. S-100β level in plasma increase in response to the acute ischemic stroke. The plasma S-100β level increases significantly in acute ischemic stroke patients when compared to the normal subjects. Beside, the plasma S-100β can be significantly correlated to the volume of infarction in brain measured by plane CT scan. Plasma S-100β is an useful biomarker in acute ischemic stroke. It can be used for estimation of volume of infarction in brain in acute ischemic stroke patients. Thus, S-100β can be used as an alternative to CT scan/ MRI in diagnosis and in taking therapeutic decision in acute ischemic stroke management.Â