The need for a robust system design is becoming increasingly important, because of the ongoing miniaturization of integrated circuits, the increasing effect of aging mechanisms, and the effect of parasitic elements, both intrinsic and external to the circuit. For safety reasons, particular emphasis is placed on robust system design in the automotive and aerospace sectors. Until now, methods to measure robustness have been applied intuitively. However, the complexity of contemporary systems makes it difficult to fulfill already tight specifications. For this reason, robustness must be integrated into a partially automated design flow. In this paper, a new approach to robustness modeling is presented, in addition to new ways to quantify or assess the robustness of a design. To demonstrate the flexibility of the proposed approach, it is adapted and applied to several different situations. These include the robustness evaluation of digital circuits under aging effects, such as NBTI; the robustness modeling of analog and mixed signal circuits using affine arithmetic; and the robustness study of software algorithms on a high system level.