Background: Out of hospital cardiac arrest (OHCA) is one of the most important medical issue, but survival rate is still extremely low. Epinephrine is essential medication in cardiac arrest. But sometimes, it is difficult to insert intravenous catheter for epinephrine while transporting. Epinephrine is also used in treating anaphylaxis. The first recommended method for epinephrine administration in anaphylaxis is intramuscular injection to thigh. Benefits of intramuscular (IM) route is as follows; 1. faster than intravenous (IV) delivery, 2. more effective than other alternative routes like subcutaneous or inhalation. Hypothesis: Intramuscular epinephrine injection can be faster alternative route in OHCA. Methods: Male Sprague-Dawley rats weighing 300-350 g were subjected to asphyxia cardiac arrest. For 72- hour survival study, 19 rats were subjected to asphyxia cardiac arrest. After 540 seconds of cardiac arrest, cardiopulmonary resuscitation (CPR) was performed and then rats were blindly allocated to one of three groups (control group, n=7; IM group, n=7; IV group, n=6). IM epinephrine (0.05 mg/Kg) or IV epinephrine (0.01 mg/kg) or vehicle (normal saline) was administered immediately with CPR, respectively. For neurological outcome study, Neurological deficit score (NDS) was measured every 24 hours after ROSC for 3 days. NDS was ranged from 0 (brain dead) to 80 (normal). Results: Between the three groups, there was no statistical difference in baseline characteristics (body weight, initial V/S, initial lab findings), time to arrest, and CPR duration. There was significant survival gain in IM group comparing with control group, but no difference with IV group in Kaplan-Meier survival curve (p=0.0076). 5 of 7 in IM group and 4 of 6 in IV group survived 72hrs. In NDS score, there was no difference between IM and IV group (72 hr NDS: IM = 44.57±12.43, IV= 46.17±15.22, p=0.8636) Conclusion: Intramuscular epinephrine increased survival rate in asphyxia cardiac arrest model of rats, and there was no significant difference in neurological function compared to intravenous epinephrine group.