Teams and teamwork are beginning to dominate industrial, academic, and military settings. Seldom are tasks accomplished by individuals acting alone. Furthermore, tasks are becoming increasingly complex with considerable cognitive demands that have rendered individual skill inadequate and have necessitated a variety of skills that are brought to the task by a heterogeneous group of specialists. Moreover, team composition changes regularly and even intact teams may experience lengthy periods without practice (e.g., incident command teams). Teams may be expected to retain teamwork skills over long periods of nonuse. The question of team skill and its decay is critical.