This paper presents a users' perspective of simulation in power electronic and motion control systems. The rationale for simulation in research, education and in the design process, and the details of how simulation is carried out are discussed. Characteristics of a reliable simulation program are outlined and the hierarchical approach to simulation is stressed. Numerical solution issues in the simulation of ”stiff” systems such as power electronics and motion control are discussed in general terms. A brief overview of the widely used simulation programs is provided along with the challenges in modeling the semiconductor devices. In conclusion, observations are made with respect to the future role and nature of computer simulations.