In Germany, 70.000 to 100.000 patients suffer from out-of-hospital cardiac arrest (OHCA) every year. More than half of these are due to cardiac causes. Despite the medical progress over the last decades, rates of survival with good neurological outcome remain low. For many below-mentioned issues, no adequate evidence from randomized trials is available. Therefore, a systematic and standardized recording of the pre-clinical, clinical and post-clinical treatment course and of the clinical outcomes of OHCA patients is essential to improve patient care. Aim of the German Cardiac Arrest Registry (G-CAR) is to achieve a better understanding of the disease entity, leading to an optimized treatment of OHCA patients. The recorded data include information on demographic and psychosocial aspects, course of the disease, clinical, laboratory and other examinations as well as treatment modalities in patients with OHCA due to a cardiac cause.