The vapour phase acetylation of benzene has been investigated over various zeolite catalysts using acetic acid as acetylating agent in a tubular reactor and at atmospheric pressure. The rate of acetic acid conversion (TOF = m mol s-' mol-' Al X 10e3) is found to be about eleven times higher over H-ZSM-5 (TOF = 46.2) compared to the H-mordenite (TOF = 4.3). HY and REY do not catalyze the reaction. The acidity of the catalysts is evaluated by the temperature programmed desorption of ammonia. NH,-TPD results show that the presence of strong Bransted acid sites are desired for the acetylation of benzene by acetic acid. The effects of time on stream (TOS), degree of Na-exchange, Si0,/A1203 molar ratios, reaction temperature, weight hourly space velocity (WHSV h-') and molar ratios of benzene/CH,COOH upon the conversion of acetic acid and product yields are investigated in the acetylation of benzene using H-ZSM-5 zeolite. H-ZSM-5 is partially deactivated under these reaction conditions. Acetic acid conversion increased with reaction temperature and benzene/CH,COOH molar ratios, whereas it decreased with the increase in reaction time, degree of Na-exchange, WHSV (h-' ) and Si02/Al,0, molar ratio. Presumably, the acetylation proceeds by the attack of an electrophile (CH3COi-) on the benzene ring resulting in the formation of acetophenone.