Therapeutic hypothermia has been shown to improve outcome in comatose survivors after cardiac arrest of cardiac origin. After the clinical implementation of this novel treatment, several international web-based registries were opened to facilitate the prospective collection of patient treatment data. The aim was to evaluate the actual use of hypothermia in clinical practice, safety aspects, resource utilization, and outcome in large cohorts of patients. There are two published studies from two separate registries, including 2205 cardiac arrest patients in 39 different sites, of whom 869 (39%) were treated with induced hypothermia. Another registry, The Hypothermia Registry, includes 1108 patients from 37 sites in six European countries and one center in the United States; a large majority, or 952 patients (86%), were treated with hypothermia. The three registries have different strengths and weaknesses, but the clinical outcome compares well with that of the two randomized trials. Our conclusions are that hypothermia is feasible to implement, that it seems reasonably safe, and that the outcome compares well with previous reports. We also conclude that the treatment with hypothermia after cardiac arrest is more widely applied than what is strictly evidence based.