Outcome from prehospital cardiac arrest was studied 1 year before (Period I) and after (Period II) a reorganisation of the work and the simultaneous change of all physicians participating in the care of prehospital patients in the emergency medical service system in Helsinki. There were 444 patients during Period I and 395 patients during Period II. Resuscitation was initiated in 279 patients during Period I and in 323 patients (P < 0.001) during Period II. The number of patients with ventricular fibrillation who suffered a witnessed cardiac arrest due to presumed heart disease was 120 and 130, respectively. During Period I, 70 of these patients were successfully resuscitated and admitted to hospital, 41 (34%) survived to discharge home from hospital. Corresponding figures during Period II were 79 and 33 (25%, NS). Compared with Period I, a larger proportion of the successfully resuscitated patients either died in hospital or were discharged to an institution during Period II (P < 0.05).