Study objective: In the present study, factors contributing to ROSC were clarified and measures to improve ROSC rates based on the Utstein style items was examined. Methods: Information from the Fire and Disaster Management Agency of japan database was analyzed. The contribution of the Utstein style items to ROSC in OHCA cases transported to medical institutions by EMT between January 01, 2010, and December 31, 2010, was assessed. Results: ventricular fibrillation ( VF ) and ventricular tachycardia ( VT ), 7.87 ( 7.09-8.72 ); epinephrine administration, 3.09 ( 2.84-3.35 ); ambulance staffed with a physician, 3.06 ( 2.69-3.49 ) were shown to be contributing factors to ROSC. Conclusions: These results showed that prompt cardiopulmonary resuscitation for VF and VT, use of an automated external defibrillator, early epinephrine administration, and development of an emergency care system in the community are important for achieving ROSC and social rehabilitation in OHCA patients.