The Zn(II)/Zn(Tl + Ga) electrode reaction was studied at the dropping Tl + Ga alloy electrode with a bulk composition of 0.06 mol% thallium in acidified aqueous 1 M NaClO4 solutions. By means of sampled de voltammetry a strongly irreversible Zn(II)/Zn(Tl + Ga) wave was obtained, which occurred around E-f(o) = - 0.989 V versus SSCE and was separated into a distinct anodic and cathodic branch. The kinetic parameters of the reaction were determined by analysis of the sampled de wave and of the ac impedance. It was found that the overall Zn(II) reduction process proceeds via the two-step electron transfer mechanism, the first step of which is rate determining in the entire accessible potential region. At the Tl + Ga electrode the rate constant of the first step A, is three orders of magnitude smaller than that observed at pure gallium. This was discussed in terms of concomitant changes of the properties of the electrode surface and its interface with the electrolyte solution. These results are hard to reconcile with current theories on the kinetics of electrochemical electron transfer reactions.