AbstractTherapeutic hypothermia (TH) is currently recommended by international guidelines in comatose patients primary resuscitated after out-of-hospital cardiac arrest (OHCA). Todays’ recommendation is that TH is initiated as soon as possible, with a temperature of 32°-34°C, and a 12-24 hours duration. In this form it has been shown to significantly increase outcome in OHCA patients, with randomized controlled trials indicating a number needed to treat of 6. However, evidence regarding specific targets in the treatment recommendations are lacking or not convincing. Thus, the aim of this literature review is to evaluate available knowledge about some specific parameters in treatment with TH after OHCA in adults: Optimal initiation time, target temperature and duration.Twenty papers were included in a literature review. It was not possible to point out a definitive time window in which TH is effective. Several animal studies show a beneficial effect of early cooling and a general deleterious effect of delay. Clinical studies indicate that both intra-arrest and post-arrest induced TH could be feasible in a clinical setting. However, clinical studies have so far failed to show beneficial effects of early cooling. Feasible cooling methods should be used in randomized clinical trials to determine the clinical time window in which therapeutic hypothermia is effective. Too deep hypothermia is probably detrimental, since animal studies show serious cardiovascular adverse effects at temperatures between 15°C and 30°C. If even milder hypothermia (36°C) is as effective as the current recommended temperature of around 33°C, is under investigation in an ongoing randomized multicenter study. There are few animal studies comparing different duration of TH after OHCA, and the study results are diverging. A recent study, however, do indicate that prolonged duration might be beneficial, and clinical studies are needed to confirm todays’ practice of 12- 24 hours cooling. Importantly, studies on TH in OHCA patients should apply a sufficient follow-up time in order to ensure correct evaluation of outcome.