PhMe, PhEt, xylenes, mesitilene, pseudocumene and 13 in-ring-substituted toluenes were oxidized with O-3 in liq. phase (AcOH or Ac2O) in presence of H2SO4 catalyst to follow the reaction kinetics and effect of substituents on the oxidn. course. The ozonolysis of the PhH ring was dominant when compared with oxidn. of the side chains. The corresponding benzoic acids prevail among the products of the alkyl group oxidn. in acetic acid.