There is a continuous recognition in the literature of residential treatment of the need for studies to assess the impact of key variables which constitute a residential milieu on the treatment environment and, by implication, on the treatment outcome. One key variable is staff cohesion. The present study explored the effect of varying levels of staff cohesion on the treatment environment in a residential treatment center for disturbed adolescents. The results suggest that the variables Support, Personal Problem Orientation, Autonomy, Practical Orientation, and Staff Control are significantly affected by varying levels of staff cohesion. However, the clients' perception of their environment did not appear to be influenced by staff cohesion level.