A natural kaolinitic clay from Padappakkara mine of Quilon District of Kerala, India, has been metakaolinized at 550 degrees C and activated separately with H2SO4, HNO3 and HClO4 of varying concentrations. The chemical composition. BET surface area, acidity distribution as well as alkylation activity of these activated metakaolinites are studied. Silica to alumina molar ratio, surface area and the number of strong acid sites increased on increasing the concentration of acid used for activation. Metakaolinite activated with 4 M HNO3 is found to possess the highest surface area and surface acidity. Alkylation of benzene with benzyl chloride at reflux was chosen as the test reaction. All the catalyst samples prepared were active for the benzylation reaction giving above 75 mol% conversion of the alkylating agent. Metakaolinite activated with 4 M HNO3 gave 87 mol% conversion of benzyl chloride to diphenylmethane with 100% selectivity within 30 min of reaction time. This could be correlated well with the greater surface acidity of this sample. It is concluded that extremely efficient solid catalysts of remarkable acidic properties could be produced by the activation of metakaolinite with H2SO4, HNO3 and HClO4.