The present study examines the building up of art classes in psychiatric hospitals in the thirties and forties of this century. Until 1950 the worldwide total of 34 art classes had come into being. The growing psychiatric interest in drawings of patients in the 19th century is related to changes in psychiatric theory moving from "moral treatment" to descriptive psychiatry at the turn of the century. All in all the installation of 11 artistic workshops for patients can be traced before the 1st world war. They were part of work therapy in german private clinics as a means to put patients of a higher social standing to a regular activity instead of field and garden work, which was medically indicated but socially unacceptable. During the course of development of a diagnostic interest since 1870 the drawings were all along considered to be the immediate expression of the patients inner world. Such a view had become possible, after in modern art the conceptions about the meaning of art had changed. Paradigmatically this connection can be shown in the work of Prinzhorn. First therapeutic attempts were then started by different psychoanalysts especially in the treatment of children. These formed an important basis for the establishment of art classes in psychiatric hospitals later on. Painting was now considered as a means to approach the hidden unconscious. The study continues to explain in which way the therapeutic applications of art therapy depended on the convergence of view points in esthetic and therapeutic theory.(ABSTRACT TRUNCATED AT 250 WORDS)