The effects of computer aided design work on the design process are analysed by field experiments. The study focuses on the influence of 3 different design tasks (standard tasks) and 11 CAD-systems (2D and 3D), taking into account the performance and strain measurements of 43 subjects (15 design engineers, 8 technicians, 17 draughtsmen, 3 trainees). The 3 standard tasks differ in performance measurements, especially in time spent on task, quantity of generated elements, not in the quality of the solution. The kind of CAD-system influences the time spent on task as well as the design performance, with significant differences of up to 100%. The same tendency can be diagnosed in a comparison of 2D and 3D systems. During the use of different functions of the CAD-system, strain effects are identified by cross-correlation with continuously measured physiological parameters, even with CAD-functions which should reduce stresses of routine work. Deficits and complications in the handling of CAD-systems increase with the complexity of the system and thus cause an antinome effect on performance and strain of its operators: creativity is reduced by frictions and frustrations in system handling even if operators are highly trained.