To assess their incidence and implications, we made a retrospective study of sudden unexpected natural deaths during driving that occurred in the five year-period between 1992 and 1997. During that period, 188 postmortem examinations were performed on driver victims of traffic accidents. Of these, 15 (8%) were found to have died of natural causes such as heart disease or cerebral hemorrhage. Marked findings in this study were that no persons over 70 years of age and more occupational drivers suffered natural death. Although no passengers or pedestrians were injured, as many as eight vehicles collided with another object or vehicle. Sudden natural death, particularly from cerebral hemorrhage, of drivers might be hazardous to other road users.