The profile of non-circular profile cams used for engine intake and exhaust control are generally finished by profile grinding using a master model. For cutting things like dies and molds, NC contouring is often employed in which the relative motion between the machine and the workpiece is directly controlled numerically, without using a mater model. Conventionally, however, NC profile machining cannot be used for high-speed machining as with copy-profiling operations although setup changes can be accomplished in a short time when shape of workpiece is changed. Recently, NC functions have been upgraded and high-speed machining equivalent to copy-profiling method is now possible. The_purpose of the study discussed in this paper is the development of a high-speed, high-accuracy NC profile grinding method for non-circular shapes. As the first step, this paper analyzes the relationship between the workpiece and the grinding wheel, using an engine intake and exhaust control cam as an example. At the same time, it also discusses profile error caused by variable factors such as wheel wear. A practical method of restricting profile error is proposed and the effects of the proposed method are clarified.