Therapeutic hypothermia for cardiac arrest survivors has emerged as a highly effective means of improving neurologic outcome. There are a number of purported mechanisms by which it is felt to be effective, but the exact mechanism is unknown. This article reviews the biochemical mechanisms of injury occurring in cardiac arrest, as well as the avenues that hypothermia takes to combat this injury. It also reviews the animal model data in support of this, as well as the newer animal studies that may help to improve the field. Several human studies of hypothermia in cardiac arrest have been performed, and this article reviews these for their methods and shortcomings. Our currently recommended guidelines for performing therapeutic hypothermia are presented. With therapeutic hypothermia comes potential risks to the patient, primarily affecting cardiac, metabolic, and hematologic systems, and these risks and their management are discussed. Multiple methods of cooling exist, including selective cranial as well as systemic cooling by internal or external approaches. Finally, the article discusses the current research in the field of hypothermia for cardiac arrest and implications for future practice.