Methane oxidation was conducted in a fixed bed quartz tubular reactor on a series of mixed oxides of cobalt/manganese prepared by a sol-gel method. A unique promoting effect of water vapor on methane conversion was observed for the first time on these cobalt/manganese mixed oxides calcined at 450 or 600degreesC. However, these mixed catalysts lost their catalytic activities after being calcined at 850degreesC. The catalytic activity of methane oxidation was significantly improved by supporting the cobalt/manganese mixed species onto the high surface area SiO2 or Al2O3-SiO2 materials. It was noteworthy that the water enhancement effect was retained on these supported catalysts. (C) 2003 Elsevier B.V. All rights reserved.