Performance analysis of plantwide control (PWC) systems, which is one of the important areas of PWC of industrial processes, has not received much attention in the past. In this paper, many measures based on plant dynamics are described and discussed for evaluating the performance of different control structures in the presence of disturbances. These include overall process settling time, dynamic disturbance sensitivity, the total variation in the plant manipulated variables, net variation from the nominal profit, deviation from the production rate target, and the integral absolute error in product purity. These measures are developed and then applied to four alternative control structures of an important industrial process, namely, styrene monomer plant, in order to test their applicability. The results indicate that some of the presented measures are indeed effective in evaluating and comparing different PWC structures. The most important contribution of this paper is the presentation of some clear and easily computable criteria for the performance assessment of PWC systems.