The anodic oxidn. of 4-chlorophenoxyacetic acid (CPA) on synthetic B-doped diamond thin film electrodes in acid media was studied, using cyclic voltammetry and bulk electrolysis. The results showed that in the potential region where the supporting electrolyte is stable, reactions occur, resulting in the loss of activity due to electrode fouling. Electrolysis at high anodic potentials in the region of electrolyte decompn. causes complex oxidn. reactions that lead to the complete incineration of CPA. There is no indication of electrode fouling under these conditions. The exptl. were compared with a theor. model. This model is based on the assumption that the electrochem. oxidn. of CPA by electrogenerated hydroxyl radicals is a fast reaction and that the process is diffusion-controlled. [on SciFinder (R)]