The desirable reaction of ethylbenzene dealkylation, accompanied by xylene isomerisation, has been studied over MFI zeolite. The effects of variation in ethylbenzene concentration in the isomer feed and the presence of paraffinic compounds on the dealkylation have been considered. Also, the undesired dealkylation of ethylbenzene during its alkylation is reported. The extent of dealkylation depends on the weight hourly space velocity, temperature and mole ratio of alkylbenzene to alcohol. The suppression of the undesired dealkylation during alkylation is discussed.