The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO[subscript]sp3-) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO[subscript]sp3- to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO[subscript]sp3- to produce an adsorbed product. An electrocatalytic link between reduction of IO[subscript]sp3- and reduction of PtO is indicated;In addition, on oxide-free Pt electrodes, the reduction of IO[subscript]sp3- is determined to be sensitive to surface treatment. The results are consistent with a mechanism involving the adsorption of IO[subscript]sp3- onto I°-covered Pt sites (Pt(I[subscript]sp ads∘)). Previous researchers have relied on chemical steps in the mechanism of IO[subscript]sp3- reduction to account for their results;The electrocatalytic oxidation of CN[superscript]- is presented as an example of anodic oxygen transfer in Part II. The electrocatalytic oxidation of CN[superscript]- is considered to be an important process for the treatment of industrial and laboratory wastes. Present electrode materials are unsuitable for CN[superscript]- oxidation for reasons of low current efficiency and high attrition rates. The voltammetric response of CN[superscript]- is virtually nonexistent at PbO[subscript]2 electrodes. Whereas the response is not improved by doping PbO[subscript]2 with Bi, the response is significantly improved by doping PbO[subscript]2 with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN[superscript]-. It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN[superscript]- is therefore considered to be a necessary prerequisite for oxygen transfer. ftn*DOE Report IS-T 1450. This work was performed under contract No. W-7405-eng-82 with the U.S. Department of Energy.