The purpose of this study was to examine the effect of persuasive communications on an individual's attitude change toward sport, which may be brought out through the study of individual's personality traits. The subjects for the study were 259 male college students. A test in attitude toward sports-manship, attitude toward winning and losing in sport, and the Japanese version of the Maudsley Personality Inventory were administered as pre-tests. One week after these pre-tests, the subjects were made to 1isten to either one of the following cassette recordings. The viewpoints of these recordings, which were different from each other, were thus; Condition A : Viewpoint affirming sportsmanship. Condition B : Viewpoint denying sportsmanship. As a control condition some of the subjects were subjected to a third condition C, where no viewpoint was presented at all. As soon as they had finished listening to the recordings the subjects were then subjected to the following post-tests: a test in attitude toward sportsmanship and a test in attitude toward winning and losing in sport. Forty-eight extraverts and 48 introverts (16 to each condition) were employed as subjects in the analysis of this study. They were chosen on the basis of their L (lie), E (extraversion), and N (neuroticism) scores in the Japanese version of the Maudsley Personality Inventory. The analysis was separately carried out on the attitude toward sportsmanship and the attitude toward winning and losing in sport, using a two-factor analysis of covariance, in which one factor was the personality groups (2), the other the persuasive conditions (3). The results obtained were as follows: 1) Concerning the attitude toward sportsmanship, the extravert group showed a greater attitude change in the direction of being persuaded than did the introvert group. This attitude change supported the proposed hypothesis. 2) Concerning the attitude toward winning and losing in sport, only under condition A, the extravert group showed a greater attitude in the direction of being persuaded than did the introvert group. From the results above it was suggested that extraverts were persuaded more easily then introverts.