Lee SY, et al. - Researchers conducted a population-based observational study for resuscitation-attempted emergency medical service– (EMS-)witnessed adult out-of-hospital-cardiac arrests (OHCAs) between 2012 and 2017 in order to determine the epidemiologic characteristics and outcome of EMS-witnessed OHCA by focusing on its prodromal symptoms. According to the patients’ chief complaints, categorization of the prodromal symptoms was done: no prodromal, respiratory, cardiac, neurologic, gastrointestinal (GI), or other symptom. The patient with multiple complaints was assigned to multiple groups. Among 12,969 eligible OHCAs, prodromal symptoms were reported in 5,246 (40.5%): 1,410 (10.9%) had respiratory symptoms, 505 (3.9%) had cardiac symptoms, 1,987 (15.3%) had neurologic symptoms, and 541 (4.2%) had GI symptoms. In cardiac etiology, best rate of survival to discharge and good neurological outcome were observed for patients with cardiac symptoms. Earlier occurrence of EMS-witnessed OHCA was observed in patients with no prodromal symptoms (5–9 min from EMS arrival) vs those with prodromal symptoms (10–14 min). Observation emphasize the necessity for promoting public awareness of prodromal symptoms to earn time for preparedness and prevention of progression to cardiac arrest.