During 1989-1991, the mobile coronary care unit (MCCU) in Gothenburg answered 10,908 calls. The most frequent cause of alarm calls was chest pain (21 per cent), whereas cardiac arrest accounted for 9 and surgical cases for 15 per cent. Severe pain was most frequent among patients with chest or abdominal pain. Despite the high frequency of chest pain, only a third of the myocardial infarction cases were attended by the MCCU. Of all cases of out-of-hospital cardiac arrest where resuscitation was attempted, 26 per cent were alive at admission to hospital, and 10 per cent at discharge, as compared with 48 and 22 per cent, respectively, among the subgroup with bystander-witnessed cardiac arrest and ventricular fibrillation as an initial finding.