The "Haus der Wissenschaften", which houses the Arbeitsgemeinschaft für Forschung in Nordrhein-Westfalen, was completed in 1960. It is not built on a grand scale, but, as befits its purpose, has been provided with a great amount of up-to-the-minute technical equipment. Its builder, who has been made a member of the Arbeitsgemeinschaft, takes this building as an example in his demonstration to other members, from other fields of science and research, of the working methods, the difficulties, the duties and the risks involved in modern architecture. Examples are given of the constructional, technical, financial, sodologi- cal, sodal and organizing sides of the master-builder's work, as also of its physiological and psychological aspects. An outline is given of the number of factors that influence him and the risks involved in calculating between them: these include tradition, experience, the results of research, scientific knowledge, emotional factors and effects, design laws artistic intention and functional demands. The importance of team-work is stressed, and team- work itself praised. Finally it is emphasized with due seriousness that, today as always, the architect and his team bear only half the responsibility. The other half lies with the man commissioning the work, not only in respect of his building programme and its requirements, but also, and this is of primary importance, of his continual cooperation in the reallzation of the building.