BACKGROUND Many patients who suffer an out-of-hospital cardiac arrest are found in electromechanical dissociation at the time the Emergency Medical Service (EMS) arrives. Since they have a poor prognosis, less attention has been paid to them. OBJECTIVE To describe a consecutive population of patients with out-of-hospital cardiac arrest found in electromechanical dissociation and to try to define indicators for an increased chance of survival in this patient population. METHODS The municipality of Göteborg. METHODS All the patients who suffered an out-of-hospital cardiac arrest between 1981-1992 and were reached by our EMS system and in whom cardiopulmonary resuscitation (CPR) was attempted. RESULTS In all, there were 3434 patients with cardiac arrest of whom 748 (22%) were found in electromechanical dissociation. They differed from patients found in ventricular fibrillation as there were more women, a higher frequency of cardiac arrest during the night, a lower frequency of witnessed cardiac arrest and consequently a lower frequency of bystander-initiated CPR. In all, 96 patients (13%) were hospitalized alive and only 16(2%) could be discharged from hospital. In a multivariate analysis relating to age, sex, time of cardiac arrest, interval between collapse and the arrival of the first ambulance, bystander-initiated CPR and treatment with adrenaline, atropine and tribonate, no independent predictor of survival was found. CONCLUSIONS Of all the patients with out-of hospital cardiac arrest in whom CPR was attempted by our EMS, 22% were found in electromechanical dissociation. Of these, 13% were hospitalized alive and 2% could be discharged from the hospital. No independent predictor of an increased chance of survival was found.