It has been argued that behavior on the Internet differs from similar behavior in the "real world" (Joinson, 1998a). In the present study, participants completed measures of self-consciousness, social anxiety, self-esteem, and social desirability, using either the World-Wide Web (WWW) or pen and paper, and were assigned to either an anonymous or a nonanonymous condition. It was found that people reported lower social anxiety and social desirability and higher self-esteem when they were anonymous than when they were nonanonymous. Furthermore, participants also reported lower social anxiety and social desirability when they were using the Internet than when they were using paper-based methods. Contrast analyses supported the prediction that participants using the WWW anonymously would show the lowest levels of social desirability, whereas participants answering with pen and paper nonanonymously would score highest on the same measure. Implications for the use of the Internet for the collection of psychological data are discussed.