The purpose of this study was to investigate the validity of hostility ratings made by others. The rating measure was considered essential for the study of correlation between hostility and coronary heart disease. Undergraduate and graduate students, 81 in all, completed a questionnaire of hostility and social desirability. The scales included were Buss-Perry Aggression Questionnaire (BAQ), Müller Anger Coping Questionnaire (MAQ), and Marlowe-Crowne Social Desirability Scale (MCSD). Acquaintances also rated them using BAQ and MAQ. Correlations between self and other ratings were moderate, and self-rated hostility scores correlated negatively with MCSD scores, while other-rated hostility scores did not. Results of ANOVA indicated that self-rated hostility scores were higher than other-rated hostility scores. However, the differences decreased as the degree of closeness between them increased, and no difference was found in long-term close relationship. These results suggested that other ratings of hostility could be an objective measure in Japan, as in western countries.