Rapid response time by paramedic units made it possible to study 26 cases of "primary" cardiac arrests occurring after arrival of the unit. Ventricular fibrillation developed in 14 cases with prodromal ectopy in only two (14%) and rapidly increasing tachycardia in seven (50%). Countershock was successful in 12 (86%) and six (43%) survived. Bradycardia and asystole following countershock forecasted a fatal outcome. Brady-asystolic arrests (BAA) developed rapidly without much warning in 12 cases and were due to sinus arrest or severe sinus bradycardia in 92% and to atrioventricular block in 8%. BAA was 100% fatal. Coronary artery disease was diagnosed as the cause of BAA in seven (58%). All of the three cases, proven to be due to coronary artery disease at autopsy, had an occlusion of the proximal right coronary artery. In the remaining five (42%) cases, BAA was secondary to ruptured aneurysm (2), acute pancreatitis (1), chronic lung disease (1), and mitral stenosis (1). These observations emphasize a need for a more aggressive approach to prehospital management of brady-asystolic cardiac arrests.