The oxidative coupling of methane has been studied at 775 degrees C on MgO, MgSO4, and Mg-3(PO4)(2) doped-by carbonates of Li, Na, K, Rb, and Cs. The conversion and selectivity on the sulfate and phosphate in the presence and absence of tetrachloromethane (TCM) as a gas-phase additive were mainly dependent on the nature of the magnesium compounds but not on that of the solid-phase dopants, while those on the oxide were influenced by the nature of the alkali metals. The influence of TCM on the methane conversion process appears to result primarily from the interaction of TCM with the anions associated with the alkaline earth compounds.