It was concluded that the presence and the protonation of the ethionine (Et) have effects on the rate of the multistep process of Bi(III) electroreduction in the 2 mol dmchlorates(VII). The catalytic activity of ethionine increases with increasing amounts of NaClO 4 in the basic electrolyte solution. Increased amounts of HClO 4 in chlorate(VII) solutions causes a decreased rate of the Bi(III) ion electroreduction process in the presence of ethionine. This confirms the assumption on the variety of active complexes mediating the passage of electrons.