A cardiac defibrillation system and method includes an epicardial electrode for making electrical contact with the epicardium from a position within the pericardial space, an endocardial electrode for making electrical contact with the endocardium of the heart, and means for making electrical contact with the epicardial and endocardial electrodes. The endocardial electrode is inserted transvenously into the heart in conventional manner. The epicardial electrode is also inserted transvenously into the heart, through the heart wall, and into the pericardial space. No open chest surgery is required.