The extent to which persons are attached to an informal work group vary and these differences are reflected in the level of group solidarity or cohesion; the higher the level of cohesion, the more likely members share attitudes and behavior expectations that influence individual task performance. Major factors involved in work group formation and cohesion encompass interaction among participants, actor discretion to carry out tasks, interdependent and interrelated work, potential group members with similar characteristics, and potential group members with personal psychological needs that can be fulfilled through interaction with group peers. The impact of informal court work groups on behavior is discussed in terms of modifying formal lines of authority, shared norms, rewards and sanctions for compliance with group norms, goal modification, and socialization. Implications of the informal work group framework for court reform efforts are considered, and benefits of using organization theory concepts to study internal operations of criminal trial courts are noted. 83 references, 4 footnotes, and 1 figure