The electrocatalytic behavior of Ti/RuO2 and Ti/IrO2 electrodes was investigated as function of the supporting electrolyte and solvent. A decrease was observed in the electrochemically active area of the electrode as the cation size increases. The oxidation potential of a series of organic solvents tested showed a straight relationship with Gutmann＇s donor number: the higher the GDN the more easily is the solvent oxidized. Oxidation of isosafrole, ISF, was used as a probe reaction to examine the influence of the supporting electrolyte cation size and the composition of the organic solvents on the electrocatalytic activity of the electrodes. The global catalytic activity for ISF oxidation is independent of the size of the supporting electrolyte cation and of the electrode material. For both electrode materials investigated it was verified that the following sequence holds for the influence of the solvent on the overall catalytic efficiency of ISF oxidation: AN > PC > DMSO approximate to DMF,