This paper describes how currently available tools for computer aided tolerancing (CAT), can be used in a two step procedure to increase the robustness of a design and when allocating proper tolerances. The first step is to increase geometric robustness by minimizing the number of parameters controlling a critical characteristic. This is closely related to the philosophy behind axiomatic design, see Suh (1990) and is performed during concept design. In this step, the CAT tool is used to analyze the general stability and sensitivity of an assembly in order to detect the sources of variation, KC:s, on an overall product characteristic, PKC. This step is performed with equal tolerances applied to all geometrical part features, which enables the designer to detect geometrical couplings and evaluate general assembly robustness. The second step is to assign tolerances on the final geometry. This is done with respect to final geometrical sensitivity, manufacturing capability and manufacturing cost and is performed during detail design. At this stage, the final variation of overall product characteristics may be simulated, and part tolerances may be adjusted with respect to final sensitivity and cost. If loss functions for the PKC:s are available, the total quality level of a concept may be analyzed.