The disproportionation reaction of toluene on synthetic zeolite-X catalysts containing various metal cations was examined using a flow apparatus. The zeolite catalysts studied showed high activities which were almost proportional to the acidities of the catalysts measured by the n-butylamine titration method (dimethylyellow indicator). The catalyst containing Cd or La ion was superior to the conventional silica-alumina catalyst both in activity and in acidity. All of the zeolite catalysts studied took some periods to be activated. Additions of benzylchloride, chlorotoluene and hydrogenchloride to the reaction system enhanced the conversions and decreased the periods of activation. Moreover, its activity increased proportionally with an increase in the amounts of hydrogenchloride adsorbed on zeolite. The results suggest that the active sites of zeolite catalyst are formed by an interaction between the zeolite cations and proton-doners.