Recently a great number of Japanese go not only to western countries but also to developing conutries, and vatious psychosomatic symptoms are seen in them while they stay overseas. But there are little published clinical data and no systematic investigations have been made as to their psychosomatic disturbances. So we tried to make a study of epidemiology of these disturbances using a personality inventory and a questionnaire on life overseas. Subjects and Method : we investigated the relationship of the TPI (the MMPI revised to assess Japanese, a 500 item parsonality inventory) and a questionnaire in regard to life and health overseas, which were administered to 162 male subjects of the Japan Overseas Cooperation Volunteers (JOCV). The TPI was given 2 months before their departure from Japan, while the questionnaire was administered on their return in 1989. JOCV members are Japanese who are sent to developing countries for a 2-year period of duty to contribute to the social development of these countries. The mean age of our subjects at the time of departing from Japan was 26.8±3.6 (M± SD) yrs. Results : 1) During their period of duty, 67(42.4%) of subjects experienced psychosomatic disturbances. The mean onset period was 6.3±5.2 months after assignment and the mean duration of symptoms was 5.4±5.0 months. 2) Items directly relatd to human relationships were rated as the main courses of strees and were higher than such items as changes in climate, weather, life style and anxiety about illness. 3) Comparing the TPI csores, it was found that the group (n=56) who strongly experienced psychosomatic disturbances, in comparison to the group (n=60) without such disturbances, had significantly (p<0.01,p<0.05) higher mean scores on the In (Introversion) scale and the Ep (Epilepsy) scale as well as significantly (p<0.05) lower mean scores on the Ma (Manie) scale. It was suggested that such disturbances were likely to be experienced by those who are introverted and sesitive, tending to suffer alone, by those who suppress feelings and are rather inflexibility in thinking, or by those who have less activities. 4) The duration of psychosomatic disturbances correlated significantly (r=0.48 : p<0.001) with the scores of the In scale. It was suggested the possibility that character tendencies before leaving Japan have some influence not only on the onset but also on the prosess of psychosomatic disturbances while overseas. 5) 12.7% of subjects strongly had feelings like persecution mania in the new surroudings while overseas; this group was significantly (p<0.01) less likely to engage in hobbies than the group without these feelings. It was suggested that enjoying a hobby is one of the effective methods in maintaining psychological health while overseas.