['Detailed procedures for optimal therapeutic hypothermia (TH) have yet to be established. We examined how duration of well-controlled core temperature within the first 24 hours after cardiac arrests (CA) correlated with neurological outcomes of successfully resuscitated out-of-hospital CA (OHCA) patients.', 'OHCA patients who survived over 24 hours and treated with TH were included. Core temperature was measured every hour. Physicians intended to maintain temperature at 33 °C ± 1 °C for 24 hours. Cerebral performance categories (CPC) of patients at 6 months were recorded and patients were retrospectively divided into favorable (CPC1,2) and poor (CPC3-5) neurological outcome groups. Total time while the core temperature reached to 33 °C ± 1 °C within the first 24 hours after CA was measured and this duration was defined that of well-controlled temperature. receiver-operating characteristic analysis was performed on duration of well-controlled temperature to select the optimal cutoff value. Neurological outcome predictors were investigated by logistic regression analysis.', 'Fifty-six patients were included. Optimal cutoff value of duration of well-controlled temperature was 18 hours. Ratio of male sex, witnessed by emergency medical service (EMS) personnel, first electrocardiogram as shockable, and duration of well-controlled core temperature ≥ 18 h of favorable neurological outcome group (n = 21) were significantly larger than that of poor neurological outcome group (n = 35). Logistic regression analysis identified "witnessed by EMS", "performed bystander CPR," and "the duration ≥ 18 h" as independent predictors of favorable neurological outcome.'] Does duration of well-controlled core temperature correlate with neurological outcome in patients with post-cardiac arrest syndrome?