This paper analyzes role transitions in small groups within the context of a more general model of group socialization that is based on the psychological processes of evaluation, commitment, and decision making. The major advantage of such an approach is that it specifies why role transitions in small groups occur. According to the model, groups and individuals change their role relationship when their levels of commitment, which are based on evaluations of readiness, cross their respective decision criteria. By examining different patterns of group and individual decision criteria and commitment levels, it is possible to differentiate various sources of strain associated with role transitions (e.g., mutual unreadiness, differential readiness, and mutual readiness), and to suggest ways in which the group and the individual might reduce such strain. This model of group socialization also may prove useful in clarifying related issues, e.g., sensitivity to strain, role transitions across external and internal group boundaries, and differential strain associated with positive and negative role transitions. (BL)