This is the first of a 2-part study on the history of psychiatry in Eastern Germany, i. e. the Soviet Occupied Zone and later German Democratic Republic. It mainly covers the years post World War II up until the beginning of the 1970s. The first post-war years were determined by the new power holders' attempts to overcome National Socialist (Nazi) heritage and to re-organize mental health and care in general. The doctrine of a strict denazifization in East Germany must, however, be regarded as a myth. Promoted by centralized organization, there was an increase in communist party-ideological influence and harassment as well as aligning scientific views and research with Soviet paradigms (Pavlovization) during the 1950s and early 1960s. This, however, led to an enormous rise in exodus of skilled labor to West Germany, which in turn further increased the notorious lack of staff. After the erection of the inner-German wall, this problem was mitigated, yet never fully solved over the 40 years of the existence of the GDR. Despite adverse conditions, East German psychiatrists made major original contributions to the development of psychiatry in general, at least up until the 1960s. Academic psychiatry was mainly based on biological concepts that were further promoted by new somatic and psychopharmacological therapeutic options. In the 1960s, social psychiatric reformist forces emerged, primarily in the large psychiatric hospitals. The improvements achieved by these forces, however, were not implemented on a nation-wide scale, but mainly restricted to one particular or several institutions.