The present research investigates relationships between group marginalization and hostility. In particular, I focus on the experiences of small, contained groups that are intentionally rejected by multiple out-group others. An integrative framework is proposed that attempts to explain how group processes influence (a) coping with threatened psychological needs following marginalization, (b) affective states, (c) cognitions regarding the marginalization and its source, and ultimately (d) hostile behavior. Study 1 describes a unique paradigm that effectively manipulates interpersonal rejection. Study 2 then implements this paradigm to empirically test relationships between the components of the integrative framework and examine differences among included and rejected individuals and groups. Results reveal partial support for the framework, particularly in regard to the impact of group marginalization on psychological needs and hostile affect, cognitions, and behaviors. Implications for natural groups such as terrorist cells, school cliques, and gangs are considered.