The catalytic influence of cysteine and cystine on mechanism and kinetics of Bi(III) electroreduction in chlorates (VII) solutions was studied. The kinetic parameters determined by using of electrochemical techniques pointed at the magnitude of catalytic effect of cysteine and cystine and allowed to achieve the mutual correlation of these values. It was found that the catalytic effect of cysteine and cystine is the biggest in 3 mol dm(-3) chlorates (VII) and that the increase of Bi(III) ions electroreduction process rate in 3 mol dm(-3) chlorates (VII) solutions is much bigger in the presence of cysteine comparing to cystine. (C) 2011 Elsevier B.V. All rights reserved.