In order to supply some informations to the preventive measures for sudden death during exercise, 167 autopsy cases of sudden natural and accidental death occurring during exercise or practice of sports were statistically and cardiac pathologically analyzed concerning the cause of death, the distribution of age and sex incidence, the characteristics of exercises, the preexisting disease and the relations between them.
　Among the cases of sudden unexpected natural death, 37.1% of all subjects in this series, the great majority of the cases was found to school boys and the causes of death in most cases (more than 80%) were sudden cardiac death. It is of interest that over half cases of sudden cardiac death were diagnosed as acute cardiac failure of unknown etiology mainly during swimming and running.
　As a lethal factor suspected of sudden cardiac death of youth, congenital anomalies of coronary arteries (abnormal origin, hypoplasia, myocardial bridge) , hypertrophic myocadiopathy, interstitial myocarditis, abnormalities of the heart conducting system and edema of the coronary wall are having a great inportance to improve the problem.
　Additionally the possibility and the difficulty of the clinical prevention of sudden cardiac death have been briefly discussed.
　As for accidental death group (62.9%), in many cases during swimming and running especially at school, acute cardiac failure might be preexisted, although the cause of death were diagnosed as drowning.

DESCENTE SPORTS SCIENCE Vol.11/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE