In this paper, we consider the effect of CH3 and OH substitution on a benzene ring in directing the site of OH radical attack in oxidative processes initiated by the gamma radiolysis of aqueous solutions of phenol and toluene. The analytical method used was micellar electrophoretic capillary chromatography. This approach permits the resolution of the radiolytic products resulting from the oxidation of the hydroxycyclohexadienyl radicals initially produced by addition of (OH)-O-. to the aromatic compounds and allows one to obtain a complete mechanistic picture of the radiation chemical processes, (C) 2002 Elsevier Science Ltd. All rights reserved.