Small groups and organizational researchers have long been interested in the process of socializing new members into existing groups. This process is believed to affect members' attitudes towards the group as well as their motivation and ability to achieve group goals. At the same time, intergroup relations researchers have long been interested in how people come to perceive in-groups differently from out-groups. Out- groups are typically perceived more homogeneously, more stereotypically, less positively, and less accurately than in- groups. However, there has been very little empirical work examining the relationship between group socialization and the development of intergroup perceptions. The purpose of the proposed research is to examine the effects of individuals' experiences as new group members, including uncertainty about being accepted by the group, interactions with full group members (e.g., hazing), and the type of information that new members encounter, on stereotype development. A longitudinal study of real-world groups is proposed in which new members' experiences are assessed and the consequences for the development of in- group-out-group differences in perceived group stereotypicality, perceived group variability, prejudice, and accuracy are examined. Two experimental studies will examine the development of new members' perceptions of in-groups and out-groups as a function of uncertainty about being accepted by the group and the type of information new members receive about the groups (i.e., group-level vs. individual-level). The outcome of this work will be a more complete understanding of group socialization, stereotype development, and the relationship between these two processes. This work may ultimately help identify ways in which groups can more effectively socialize new members and promote more positive and constructive intergroup perceptions. As a result, the anxiety associated with new membership in work and social groups, as well as the negative effects of stereotyping on individuals' psychological well-being, are likely to be reduced.