To clarify migrant population characteristics, we examined the relationship between out-migration from study areas during a 3 year follow-up period and health status, life style, and socioeconomic factors obtained at the initial baseline survey in a cohort study involving 15, 493 males and 17,440 females. Characteristics of inter-prefectural out-migrants were summarized as follows: 1) A significantly higher proportion of inter-prefectural out-migrants were employees of relatively large companies, family members of these employees, white collar workers in the case of males, and housewives in the case of females. 2) Inter-prefectural out-migrants had relatively good health status and high participation in cancer screening tests. 3) The dietary habits of inter-prefectural out-migrants were more westernized and well-balanced. 4) Male inter-prefectural out-migrants had a higher proportion of heavy smokers and daily drinkers, while females had lower proportion of smokers and drinkers. When comparing in-migrants to out-migrants, the characteristics were similar for males, but opposite for females.