Fifty-five Veterans Administration hospital wards with widely varying size and staffing were studied in an attempt to relate these ecological ward characteristics to perceived treatment environments. It was hypothesized and confirmed that both size and staffing were independently related to treatment environment. As size increased and staffing decreased the emphasis on relationship dimensions of Support and Spontaneity and treatment program dimensions of Autonomy, Practical Orientation, Personal Problem Orientation, and Anger and Aggression tended to decrease, whereas the amount of emphasis on Staff Control tended to increase. The results provide information about the mediating variables by which increased size and decreased staffing tend to have their effects and indicate that both ecological and psychosocial variables must be assessed in studies of ward treatment environments.