Today overseas activities by the Japanese are increasing rapidly. The onset of psychosomatic disease by culture shock in Japanese people living overseas is becoming a major problem. However, there is very little clinical investigation of this problem. Therefore, we conducted a psychosomatic research for the past 7 years from 1980 to 1986 in 4091 Japanese people of the Japan Overseas Cooperation Volunteers(JOCV), who left Japan for overseas service and lived in 35 different developing countries in tropical and subtropical zones. JOCV is a volunteer group of men and women with ages 20-35 who are sent to developing countries in Africa, Asia, Latin America, Middle East and Oceania for 2 years for the purpose of contributing to the social development of these countries. Of these 4091 volunteers, there were 172 who have returned to Japan for some clinical reasons during their terms of service. Among them those who came back because of the onset of psychosomatic diseases (PS group) or of mental disorders (MD group) were subjected to our present study. (1) The PS group consists of 37 case (among them 19 were women) and the MD group consists of 12 cases (among them 3 were women). The average age of the PS group was 25.1±2.8 years old (m±SD) and that of the MD group was 27.1±3.5 years old (Tab.1). (2) As to the presence of past history of the same symptom before leaving Japan, it was found in 29% of the PS group while none was in the MD group. (3) After leaving Japan, the average time before the onset of disease was 7.4±5.9 months (m±SD) in the PS group and early onsets of within 6 months were found in 51%. As to the MD group, the average time of onset after leaving Japan was 11.8±7.4months (m±SD) (Fig. 1). (4)The results of TPI test (Todai Personality Inventory test; a questionnaire including 500items) applied before leaving Japan, were compared in terms of Hypochondriasis (Hc). A total of 37 patients, the sum of PS group (25) and MD group (12), showed significantly higher scores (p<0.01) than the healthy 37 controls who were matched with the 37 patients by age, sex, country visited, year of visit and type of job. From these results, it was suggested that volunteers with highly hypochondrical tendency show a higher incidence of psychosomatic or mental symptoms in overseas (Tab. 2). (5)As to the ratio of number of cases among the PS group to that of total volunteers, African zone has a significantly higher (p<0.05) in number than other zones. This can be attributed to the seriously poor conditions of medical care in the African zone compared with those of other zones (Tab. 3).