Toluene has been alkylated with methanol over Y-zeolite catalysts to produce p-xylene. The experiment was carried out continuously over fixed bed catalysts under atmospheric pressure. The selectivity for a specific xylene isomer was demonstrated to undergo a remarkable change depending on the experimental conditions such as temperature, space velocity, and reactant ratio in the feed. At thermodynamic equilibrium at 350 ℃ of optimum reaction temperature, the xylene mixture contains about 20 % of p-xylene, while in this study the product mixture consisted of 47 % of p-xylene. It has been found that HX-zeolite has a high selectivity and HY-zeolite a high activity, whereas both HM-zeolite and silica-alumina have low activities The optimum reaction conditions were as follows ; reaction temperature of 350 ℃, toluene/methanol mole ratio of 2, and space velocity of 0.48 l/gr-cat/hr. At relatively high reaction temperatures, Y-zeolite catalysts produced the mixture of xylene which composition corresponds closely to thermodynamic equilibrium values. The main products were xylene, trimethylbenzene, and benzene. The products were analyzed by gas chromatography. As a promoter, BF₃ and WO₃ were added to the main catalysts in order to understand the effect of supports on the formation of xylene. When the content of BF₃ supported on HY-zeolite was 2 wt%, the yield of p-xylene was increased from 8.6 % to 13.7 %. For WO₃, with 5 wt% of WO₃ the yield of p-xylene was increased from 8.6 % to 13.8 %. In order to know the effect of Brönsted acid on the yield of p-xylene, HCl was added to HFeY catalyst. As the content of p-xylene was 6 wt% with respect to methanol, the yield of p-xylene was increased from 15.7 % to 19.7 %.