We examined the performance of a hospital-based mobile coronary care unit staffed by emergency physicians, coronary care nurses, and ambulance personnel in a metropolitan setting (Brisbane, Australia). Our unit attended 2,260 calls during 18 months of operation. Standard dispatched ambulances arrived first to 78% of the 2,260 calls. Ten percent of these calls were to patients who had died or had arrested; 45% of these patients were found in ventricular fibrillation and 10% were discharged alive from the hospital. Survival was related to the performance of CPR before the arrival of the unit and to the finding of ventricular fibrillation. As the success of our unit was clearly inferior to that reported from centers where the first-responders are licensed to defibrillate, its operations have ceased and regular ambulance crews are being taught to recognize and treat patients with ventricular fibrillation.