MoO3 and V2O5 were deposited on the Au anode of the electrochemical reactor using yttria-stabilized zirconia as a solid electrolyte, and oxygen was pumped to each metal oxide through the YSZ by closing the electrical circuit. The system was used for the oxidation Of C-2-C-4 hydrocarbons over MoO3 and V2O5 under the oxygen pumping conditions at 500 degreesC. Alkanes were,, while alkanes were not oxidized at all but alkenes were selectively oxidized to the corresponding aldehydes over MOO, activated to initiate the oxidation reaction and alkenes were deeply oxidized over V2O5 Over MoO3, the highest selectivity to aldehyde was observed with isobutene (methacrolein) followed by propene (acrolein) and ethene (acetaldehyde). In the oxidation of alkanes over V2O5 the rate of reaction was logarithmically well correlated with the C-H bond energies of alkane, suggesting that the rate-determining step is H-abstraction from alkane. In both cases of using MoO3 and V2O5, a co-presence of gaseous oxygen with hydrocarbons resulted in decreasing selectivity of the aldehydes. It is likely that the oxygen species derived from the lattice oxygen of YSZ migrates to MoO3 and V2O5 and the activity for the selective oxidation of hydrocarbons depends on the nature of each metal oxide catalyst.