The livedo is a purplish erythema forming more or less regular mesh on the skin. This phenomenon is caused by blood deoxygenation and stasis in the dermal venules. It is important to differentiate between a benign form, usually associated with cold exposure, and a secondary form necessitating further investigations of an underlying disease. The purpose of this article is to discuss the pathophysiology and causes of this phenomenon. Treatment is not covered in this article because of its complex and often multidisciplinary approach.