Therapeutic hypothermia has been shown to improve survival and neurological outcome after prehospital cardiac arrest. Existing experimental and clinical evidence supports the notion that delayed cooling results in lesser benefit compared to early induction of mild hypothermia soon after return of spontaneous circulation. Therefore a practical approach would be to initiate cooling already in the prehospital setting. The purpose of this review was to evaluate current clinical studies on prehospital induction of mild hypothermia after cardiac arrest. Most reported studies present data on cooling rates, safety and feasibility of different methods, but are inconclusive as regarding to outcome effects.