The following fields of application, belonging to the social behavioral sciences are mentioned: 1 The organisational structure of the psychiatric hospita!. 2 The psychiatric hospital as a therapeutic community. 3 Treatment and approach of the mentally deficient. With regard to the connection between structure and function of the psychyiatric hospital special attention is paid to the rehabilition of the hospitalized patients. From literature-data and on the strength of own experiences within the psychiatric hospita! „Veldwijk" in Ermelo these aspects are explained more fully.