We investigated 303 (men: women = 2:1) cases who suffered sudden heart arrest in Yamagata city since 1984 to 1987. The incidence rate was 41.0/100,000/year, and increased markedly with increasing age. There was a tendency for sudden death to occur in the winter season, evening and early morning. Two major causes were cardiac disease (especially ischemic heart disease) (46.4%) and intracranial hemorrhages (18.6%). 20% of all the heart-arrest cases were able to be saved, but, depending on the kind of heart disease the survival rate varied greatly (18.8% in acute myocardial infarction and 71.4% in vasospastic angina), (40.0% in ventricular fibrillation and 13.3% in the bradycardic arrhythmias). Survival rate was also effected by the time interval from the onset till the beginning of cardio-pulmonary resuscitation. About one half of the cases had histories of cardiac disease. Premonitory symptoms were observed in at least one third of the cases.