Functionalism serves as the guiding concept of this piece of work, on the example of which shall be traced the changes that took place in modern architecture between 1930 and 1950. This choice seems appropriate since Functionalism is a particularly relevant yardstick of the state of modern architecture owing to its radical nature. In its generally accepted form, Functionalism embodies the most rigorous stage of a development that in the early 1920s assumed a variety of forms, that became increasingly strongly focussed, and which finally expanded in the early 1930s. On the other hand, a penetration of the core of the concept of Functionalism is an uphill task and demands an investigation into allied concepts such Objectivity, and in particular the New Objectivity, Neues Bauen and Rationalism, as well as a digression into Italian Razionalismo. This exploration is followed by an attempt to define Functionalism, whereby the intention is not to equate it with the status of "dogmatic Functionalism" with which its condition at the end of the 1920s shall be labelled, but to attempt to understand it in a more comprehensive sense. This extended view of Functionalism forms the basis of an analysis of the expansion stage, which can be divided into three parts for which the following concepts stand: "enlightened Functionalism" for the years from 1930 to 1935, "self-evident Functionalism" for the following period up until the end of the war, and "subliminal Functionalism" for the first post-war years until 1950 – concepts that refer to the types of development in which Functionalism continued to forfeit its radicality and mutate into an undogmatic, widely accepted form of modern architecture. Towards 1950, however, functionalistic methods were more and more frequently overlaid by a traditional language of form that increasingly blurred the contours of functionalist aesthetics. This represented the final stage of development, for an invisible functionalism is no longer an "ism" – and thus no longer Functionalism. Buildings from Switzerland and Sweden provide the main source of illustrative material, despite the fact that Functionalism developed in Germany. This is connected with the architectural quality of Swiss and Swedish building at the time, as well as with the changes in the political situation. For although World War II brought about a crucial break in Switzerland and Sweden, it did not call a complete halt to the previous developments as it did in most other European countries.