Objective: To clarify the relationships of the rationality/antiemotionality (R/A) personality with past histories of seven chronic diseases and current smoking habits in a community population in Japan. Methods: A questionnaire survey was conducted of all residents aged 35 years old or over (n = 37,287) in Takayama city, Gifu prefecture, Japan; the response rate was 90.3%. Data from 13,091 males and 14,061 females who completed all relevant questions were analyzed. The subjects were asked to complete an 11-item R/A personality scale developed by Grossarth-Maticek et al. (1985). Past histories of seven major chronic diseases and current smoking habit were also asked in the questionnaire. Results: Among males, the R/A scale score was significantly lower in those who had stroke, diabetes or allergy than in those who did not. Among females, the R/A scale score was significantly lower in those who had stroke, allergy or stomach cancer than in those who did not. Among females, current smokers had significantly lower R/A scores than non-smokers. After controlling for age, smoking and drinking, the R/A score was significantly and negatively associated with stroke among males and females; it was significantly and negatively associated with diabetes and allergy among males. Conclusion: Our findings are contrary to those observed in Yugoslavia and West Germany, and suggest a cultural difference in the relationship between the R/A personality and disease occurrence. (C) 2000 Elsevier Science Inc. All rights reserved.