Hospital mortality was examined in all patients successfully resuscitated from a witnessed out-of-hospital cardiac arrest due to ventricular fibrillation over a 1-yr period. Variables independently predictive of hospital mortality were a history of congestive heart failure before cardiac arrest, the time between collapse and initiation of CPR, and the time between collapse and restoration of circulation. The latter time was not related to either patient age or clinical history. Thus, hospital mortality was predetermined by prehospital factors, some of which can be changed.