"Toluene Disproportionation" reaction, is an industrial approach for the production of benzene and xylenes from toluene. Xylenes are important materials for production of chemicals and petrochemicals. In recent years, because of an increase in P-Xylene worldwide demand, this reaction has a special importance in industrial applications. In industrial processes, this reaction can be carried out in fixed bed reactors and over acid zeolite catalysts. Two major processes that operate basically on this reaction, are "Tatoray" and "PX-Plus". In this work, these processes are described and the reactors are modeled mathematically. The model results are compared with experimental data (reported by other researchers) and the models are verified. Optimization of reactors with mathematical model, is another purpose of this work that is achieved. Finally, reactors are compared in optimum operational conditions. Results of this comparison , are summarized below: · For both processes, toluene conversion is about %(30 5). · In PX-Plus Process, P-Xylene Yield is higher than Tatoray Process. · Para-Selectivity for PX-Plus process is about %90. · In PX-Plus process, Benzene/Xylene molar ratio is higher than tatoray process. · To achieve optimum conditions, PX-Plus process needs higher temperature and higher residence time than Tatoray process.