This study is concerned with the contouring control of biaxial motion systems. It is well known that contour errors depend not only on the controller, but also on the reference command. Two problems are investigated in this paper. First, it is to find the reference command that will yield the minimum contour error. This is the problem of interpolation and acceleration/deceleration. Second, given a reference command, it is to find a modified reference command so that the system output will be as close to the reference command as possible. The design of the modified reference command utilizes the inverse model of the closed-loop system. In other words, the modified reference command can be considered as the output of the inverse system with the desired reference command as the input. It can be obtained by the convolution technique.