A practitioner's first exposure to group therapy becomes a template from which future practice is derived. In particular, the group format and the degree of structure imposed by the leader on the process are imprinted in the leader's clinical reasoning. Group therapies are commonly categorized as psychodynamic, interpersonal, cognitive, and behavioral. Each of these conceptual frameworks indicates the group's composition, leader role, and intervention principles. By carefully considering the degree of structure imposed, rather than follow implicit knowledge of past experience, the leader can more consciously shape group outcomes. The author proposes a rehabilitation paradigm, the Functional Group Model as a theoretical basis for determining the degree of structure as a component of the group design. The assumption underlying the model is that by changing the degree of structure a leader can facilitate outcomes such as group cohesion. Inevitably group format influences the degree of activity and inactivity of the leader.