<p>Relationships among social anxiety, fear of negative evaluation from others, avoidance behavior, and self-disclosure were investigated. Undergraduate students (n=308) completed self-report measures assessing the above factors. The results of cluster analysis by the Ward method showed that social anxiety, fear of negative evaluation from others, and avoidance behavior were composed of three clusters: Low social anxiety, Moderate social anxiety, and High social anxiety. A one-way analysis of variance conducted on these clusters indicated that the High social anxiety cluster had lower self-disclosure scores concerning hobbies, and difficult experiences, compared to the other clusters. Moreover, the multiple regression analysis showed that avoidance behavior had significant effects on each type of self-disclosure. These findings suggest that the reduction of avoidance behavior might affect the increase of self-disclosure.</p>