The electrochemical behavior of molten K2S2O7 and its mixtures with V2O5 [2-20 mole percent (m/o) V2O5] was studied at 440 degrees C in argon, by using cyclic voltammetry on a gold electrode. The effect of the addition of sulfate and lithium ions on the electrochemical processes in the molten potassium pyrosulfate was also investigated. The potential window for pure K2S2O7 was estimated as 2.1 V, being limited by the S2O72- oxidation and reduction. The oxidation of SO42- to oxygen is reversible in the basic melt. It is found that V(V) electroreduction proceeds in two steps. The first reduction stage [V(V) --> V(IV)], starting at 0.7-0.8 V vs. Ag+/Ag, is reversible for V2O5 concentrations lower than 5 m/o and at potential scan rates less than 200 mV/s. For all studied compositions, the first reduction stage is a one-electron reaction. The second reduction stage [V(IV) --> V(III)], starting at 0.1-0.2 V, is irreversible and under ohmic control at all studied V2O5 concentrations. The presence of Li2SO4 causes a noticeable depolarization effect on the V(V) reduction and the V(IV) oxidation.