A computer model was developed to simulate the performace of three commercial reactors in series for dehydrogenation of ethylbenzene to styrene. The model can be used to predict the performance of dehydrogenation catalysts in the commercial reactors. In the model program, flow of the reactant stream through the catalyst bed is treated as one-dimensional plug flow. The kinetic rate parameters were obtained by using the Conjugate Direction method as a multivariable search technique so as to minimize the sum of squares of differences between predicted and actual conversions. The predicted conversions were found by numerically solving the differential equations for pressure gradient, energy, and material balances for the main reaction and five side reactions. The results indicate reasonably good simulation of the new plant data as a test of the model. Various catalyst and reactor combination schemes will later be used to optimize overall plant performance by means of computer model developed.