Acylation of toluene with acetic anhydride was carried out over Beta-type zeolites in a stainless steel autoclave. At low temperature, i.e., 150 degrees C, and an arene/anhydride molar ratio 10-20, high yields of 4-methylacetophenone were obtained with selectivity close to 100%. The reaction is limited by the poisoning of the active sites by adsorption of the product and pore blockage due to "coke"-type products. Acid site accessibility is of paramount importance for this reaction, and the use of a nanocrystalline Beta zeolite as catalyst minimizes catalyst decay. This, combined with an optimum framework composition, allows the preparation of active and selective acylation catalysts based on Beta zeolite.