The electrochem. oxidn. of 3-methylpyridine (3-MP) at synthetic boron-doped diamond (BDD) thin film electrode was studied in acid media by cyclic voltammetry and bulk electrolysis. The results showed that in the potential region of water stability there can occur direct electron transfer reactions on BDD surface that result in electrode fouling due to the formation of a polymeric film on its surface. While during electrolyzes in the potential region of water decompn., indirect oxidn. reactions can take place by electrogenerated active intermediates, probably hydroxyl radicals that can avoid electrode fouling. Depending on the values of applied c.d., it is possible to obtain the partial oxidn. of 3-MP to nicotinic acid or the complete combustion of 3-MP to CO2. [on SciFinder (R)]