The electrochem. oxidn. of phenol at synthetic boron-doped diamond thin film electrode (BDD) was studied in acid media by cyclic voltammetry, chronoamperometry, and bulk electrolysis. In the potential region of water stability (E <2.3 V vs. SHE) they can occur direct electron transfer reactions on BDD surface that results in electrode fouling due to the formation of a polymeric film on its surface. While during electrolyzes in the potential region of water decompn. (E >2.3 V vs. SHE), indirect oxidn. reactions can take place by electrogenerated active intermediates, probably hydroxyl radicals, which can avoid electrode fouling. Depending on the values of applied current, and phenol concn. it is possible to obtain the complete combustion of phenol to CO2 or the partial oxidn. of phenol to other arom. compds. (benzoquinone, hydroquinone, catechol). [on SciFinder (R)]