To clarify major social risk factors affecting the mortality from motor vehicle accident (MVA), we analyzed the effects of a wide variety of socioeconomic and demographic indicators (20 variables) on age-specific and age-adjusted mortality rates from MVA in 46 prefectures in Japan. The analysis was conducted twice at a 5-year interval, i.e., in 1970 and 1975, by stepwise regression analysis after classification of the indicators by factor analysis. The major social risk factors identified in the two years were as follows: (1) rural residence for persons, especially males, of major driving age (15-54 years) and young male children (0-4 years); (2) population growth by social mobility for schoolboys aged 5-14 years; and (3) high income (and employment) for schoolgirls, and proportion of old population for middle-aged females. Age-adjusted male rate of mortality from MVA within 46 prefectures was significantly higher in rural than urban areas in both 1970 and 1975.