The oxidative coupling of methane to ethylene and ethane was studied over lithium-cerium-promoted MgO and MgO-CaO catalysts in the presence of molecular oxygen at 730 degrees C and at atmospheric pressure in a continuous how, fixed bed quartz reactor. The catalysts were prepared by an impregnation method and finally calcined at 900 degrees C. The surface area, pore size distribution and pore volume of the catalysts were determined. The feed consisted of only methane and oxygen in the molar ratio of 2:1. The results obtained over the catalyst systems, viz. (i) lithium-cerium-promoted MgO and (ii) lithium-cerium-promoted MgO-CaO, have been compared. A relatively high C-2-selectivity has been obtained with Li-Ce-promoted MgO-CaO catalysts. The optimum yield and selectivity for C-2-hydrocarbons were found to be 21.5% and 76.8% respectively at a methane conversion of 28% over Li (7 wt%)-Ce (2 wt%)-doped MgO-CaO (3:1 wt ratio) catalyst. The various factors governing the activity and the selectivity of the catalyst systems have been discussed.