Reactive Yellow 3 dye was electrooxidized at Pt and electroreduced at hanging Hg drop electrode to study the course of the reactions. The electrode reactions were irreversible and diffusion-controlled. The amino group and/or the bond between C atom in PhH ring and N atom in the azo bond in the dye mol. were converted by the electrooxidn. The dye redn. was more complicated due to the presence of azo and triazine groups. The azo bond electroredn. was influenced by pH and proceeded faster in an acidic medium.