The purpose of this study was to evaluate the reliability and validity of the Korean version of the Temperament and Character Inventory (TCI), a self-report questionnaire based on Cloninger's biosocial model of personality. The TCI was translated into Korean and administered to 851 Korean college students. A test-retest study of the TCI was conducted across a 3-month interval with 130 subjects. Internal consistency was calculated by Cronbach α. Test-retest reliability was analyzed by Pearson correlation analysis. Factor analyses for the temperament and character dimensions were performed using principal component analysis, rotating factors obliquely by promax. A comparison of TCI scores between Korean and United States college students was done using independent t tests. Cronbach α values for the TCI scales ranged from .60 to .85 for the temperament scales and from .82 to .87 for the character scales. Test-retest correlations (r) ranged from .52 to .72 for the temperament scales and from .52 to .71 for the character scales. Principal component factor analyses showed similar factor structures of four temperaments and three characters as the American version of the TCI, except for the Reward Dependence and Persistence temperament scales. Explorative factor analysis with a condition of eigenvalue greater than 1 produced five factors, as compared to seven factors extracted in Cloninger's original report. Results using a preset seven-factor solution was forced and did not successfully extract Cloninger's seven factors. Korean college students had higher mean scores on Harm Avoidance and lower mean scores on the rest of the scales as compared to a sample of US college students. The results of this study confirm that the Korean TCI has satisfactory psychometric properties and reflects Cloninger's biosocial model of personality.