Objectives/Hypotheses 1. Prehospital termination-of-resuscitation (TOR) rules were developed in North American and European sites. Whether they remained valid in different geographic, ethnic, and cultural background areas is still under debate. 2. Differences in characteristics of out-of-hospital cardiac arrests (OHCAs) and configurations of emergency medical service (EMS) between the Western and Asian countries, including relatively lower rate of presenting shockable rhythm (i.e. ventricular fibrillation / ventricular tachycardia; VF/VT), lower rates of bystander CPR, less advanced life support (ALS) implementation, and less public access defibrillators, might create potential threats to the prediction accuracy of TOR rules. 3. We aim to conduct a study to validate the performance of ever published TOR rules in Asian OHCA population, including non-traumatic, traumatic, and pediatric OHCA patients. Furthermore, assess the possible variables that may impact the performance of TOR rules. 4. We also aim to develop new TOR rules based on PAROS registry for Asia population, focusing on non-traumatic, traumatic, and pediatric OHCA patients, respectively.