The behaviour of Cu(ClO4)(2), CuCl2 and CuBr2 in 20 wt.% propylene carbonate (PC)+ ethylene carbonate (EC) has been studied by conductivity, potentiometry and voltammetry. The conductance behavior of copper(II) halides in 20 wt.% PC + EC is explained on the basis of the equilibrium 3CuX(2)reversible arrowCu(2+) +2CuX(3) and 2CuX(2)reversible arrow(CuX2)(2). A copper indicator electrode in conjunction with a Hg/HgCl2(s) in 20 wt.% PC+EC reference electrode was used for the potential measurements. The results of the potentiometric measurements, combined with those of the conductance measurements, provided the standard potential, Edegrees, of the reaction Cu2+ + 2e(-)reversible arrowCu(s) versus SHE in 20 wt.% PC+EC at 25 degreesC, which is found to be 0.400+/-0.002 V. Sampled dc and cyclic voltammetric measurements were also undertaken with these Cu(II) salts in 20 wt.% PC+EC using Pt working and counter electrodes and Hg/ HgCl2(s) in 20 wt.% PC+EC as the reference electrode. These voltammetric measurements yielded the standard potential value (0.394+/-0.003 V vs. SHE) of the system, which is in agreement with the value obtained by the potentiometric method.