The syntheses of diaryliodonium salts by the anodic oxidation of an aryl iodide in the presence of an arene in solvents containing acetic acid, acetic anhydride, and an acid are investigated. The influence of the reaction conditions on the yield of the 4,4'-dimethyldiphenyliodonium cation from the electrolysis of solutions containing both 4-iodotoluene and toluene is explored. The reaction gives good yields of diaryliodonium salts for aryl iodides and arenes with alkyl substituents. The factors that limit the extension of the reaction to other functional groups are discussed.