Abstract. In this article, we investigate the effects of avatars appearance on user sociability in 3D virtual worlds. In particular, we study gender and appearance differences in social communication preferences and behavior in virtual public spaces. For this purpose, we have employed the virtual ethnographic method, which is an adaptation of traditional ethnography for the study of cyberspace. Although we only employed nine users who used four different avatars, we observed a cumulative of more than two hundreds social encounters. We found that users with more elaborate avatars had a higher success rate in their social encounters, than those users with the default avatars. Most notably, female users selected to speak with male avatars much more frequently, when using the attractive avatar, which indicates a self-confidence effect induced by the appearance of the personal avatar.