Diethyl carbonate (DEC) has been produced by the oxidative carbonylation of ethanol in the gas phase over a heterogeneous CuCl2/PdCl2 catalyst supported on activated carbon. Yields of DEC with this catalyst are approximately 10 wt % with the byproducts diethoxymethane, ethyl formate, and acetaldehyde also formed in significantly lower yields. Treatment of the catalyst immediately after preparation with potassium hydroxide enhances the production of DEC almost 2-fold without increasing the amount of byproducts formed. The reactions that form DEC and the byproducts occur in a parallel, rather than a sequential, manner indicating that it should be possible to identify a catalyst which is more selective for DEC.