In social psychology, two forms of attachment to groups are distinguished: interpersonal attraction and social identification. A web experiment was conducted to examine whether these two forms of attachment can also be differentiated in virtual communities, more precisely, MUDs (multi-user-dungeons). Both forms of attachment occurred. As expected, the concepts were functionally independent from each other. Whereas interpersonal attraction became stronger with increased duration of group membership and was fostered by physical life contacts, social identification was independent from these factors. Instead, social identification was related to more cognitive indicators of self-categorization. In contrast to interpersonal attraction, social identification was influenced by situational context and predicted group behavior such as ingroup bias. (PsycINFO Database Record (c) 2012 APA, all rights reserved)