Admission to hospital for psychotherapy facilitates communication with patients and allows more ways of influencing them than do conventional out-patient situations. Small and large groups can be added to individual interviews, and living together allows the development of many potentially therapeutic relationships with other patients and staff. This additional influence can be ignored. If it is assumed to be an integral part of treatment and organised rationally, the whole hospital becomes its instrument; psychotherapists, nurses, patients, domestic staff and administrators can be seen to be subordinate to that whole, and their traditional activities, attitudes to each other, and theories, are inevitably modified. Traditional boundaries between the roles of different workers become blurred, while how they get on with each other has important consequences for patients, so that their separate roles and functions must be clearly defined.