This paper presents a commentary on the status of application of modern control theories to industrial chemical processes. The difficulties encountered in the implementation of advanced control to chemical reactors are critically examined in order to determine the reasons for its limited success to date. Chemical processes, very often poorly understood because of the physicochemical complexities, are nonlinear, highly interacting, spacially dependent, and continuously disturbed by many uncharacterized noises. It is time-consuming and expensive to develop advanced control methods for these systems because few of the available theories can be applied directly. Thus, we often find it difficult to economically justify advanced control projects.