Extracranial carotid stenosis is a well-established, modifiable risk factor for stroke. Asymptomatic extracranial carotid stenosis is increasingly being detected due to the introduction of less-invasive and more-sensitive advanced diagnostic technologies. For severe asymptomatic stenosis, earlier pivotal clinical trials demonstrated the benefit of carotid endarterectomy over the best medical therapy. Since then, great advances have been made in interventional and medical therapies as well as surgical techniques. The first edition of the Korean Stroke Clinical Practice Guidelines for primary stroke prevention for the management of asymptomatic carotid stenosis reflected evidences published before June 2007. After the publication of the first edition, several major clinical trials and observational studies have been published, and major guidelines updated their recommendation. Accordingly, the writing group of Korean Stroke Clinical Practice Guidelines (CPG) decided to provide timely updated evidence-based recommendations. The Korean Stroke CPG writing committee has searched and reviewed literatures related to the management of asymptomatic carotid stenosis including published guidelines, meta-analyses, randomized clinical trials, and nonrandomized studies published between June 2007 and Feb 2011. We summarized the new evidences and revised our recommendations. Key changes in the updated guidelines are the benefit of intensive medical therapy and further evidence of carotid artery stenting as an alternative to carotid endarterectomy. The current updated guidelines underwent extensive peer review by experts from the Korean Stroke Society, Korean Society of Intravascular Neurosurgery, Korean Society of Interventional Neuroradiology, Korean Society of Cerebrovascular Surgery, and Korean Neurological Association. New evidences will be continuously reflected in future updated guidelines.