Two studies were performed to assess the validity of a World-Wide Web (WWW) measure of self-monitoring. In Study 1, Usenet Newsgroups likely to be read by high and low self-monitors were identified and a comparison was made of the extent to which contributors engaged in a form of self-presentation (use of handles or screen names) likely to be influenced by self-monitoring tendencies. Handles were used significantly more frequently in the high self-monitoring Newsgroups, supporting the distinction made. In Study 2, participants recruited through these sets of Newsgroups completed the WWW-mediated test. Those from the high self-monitoring groups scored significantly higher. Self-reports of self-monitoring behavior also reflected scores on the scale. The results are interpreted as demonstrating the construct validity of the instrument used and the viability of criterion-group-oriented methods in Internet-mediated research.