After a short explanation of some key concepts in behavior therapy the author describes three ways of introducing behavior therapy in a psychiatric hospital: a) to set up separate behavior therapy departments in which one of several techniques are used b) to bring patients together in groups for part time behavior therapy. c) to integrate behavior therapy programs into departments, that are not specifically oriented towards behavior therapy. a) is illustrated by a short description of the token-economy department of the hospital; b) is illustrated by an example; c) is the most difficult procedure because it requires both detailed behavioral diagnosis and accurate cooperation of all staff members who interact with the patient. Part of a case history serves as illustration. The author further points out that behavior therapy and drug treatment are far from antogonostic. On the contrary: both tend towards modification of concrete behavior patterns i.c. both are behavior-oriented rather Man disease oriented. The author concludes that behavior therapy is a very important therapeutic asset; introduction into the mental hospital is a complex and difficult task however because the application of behavior therapy requires a high level of information and competente of all staff members.