The resuscitation experience of a large teaching hospital during 1973-77 was reviewed. Resuscitation was attempted on 2091 victims of cardiac arrest; 261 patients (12.5%) survived to be discharged from hospital.Coronary heart disease caused about one half of all the cardiac arrests, but was associated with a better survival rate (14.4%) than the other causes. Cardiac arrest following multiple trauma had the worst prognosis; only 3% of the patients survived to be discharged from hospital. However, the main factor influencing outcome was the site of arrest. The survival rates of patients on whom resuscitation was initiated in the emergency room or an intensive care area were triple and double the rate for patients in hospital wards, although one third of all the cardiac arrests induced by a coronary event and occurring in hospital were on the wards. Patients whose arrest occurred outside hospital, where only basic life support was available, had a survival rate of just 6.3%, whereas those whose arrest occurred in the emergency room had a survival rate of 31.9%. Since these two patient groups were similar in terms of age and diagnosis, we believe that the potential survival rate for victims of cardiac arrest outside of hospital that are optimally treated is close to 30%.These data suggest that increased survival from cardiac arrest can be expected with extension of the resuscitation services both inside and outside of hospital, but particularly with increased emphasis on emergency cardiac care outside of hospital.