The catalytic production of gas-phase methyl radicals from methane over the lanthanide oxides was measured by using a matrix isolation electron spin resonance (MIESR) technique. The results show that metal centers with multiple stable oxidation states are not a requirement for activity. The oxide with the greatest activity per gram was hydrothermally treated La203, which was ca. 5 times more active than the next highest oxide. Hydrothermally treated La203 and Sm203 have the largest activities per square meter. Results obtained in a conventional flow reactor for selected oxides indicate that the CH4 conversions per square meter are in the order Nd203 > La203 > Sm203 > Dy203 > Ce02. Oxidative coupling of CH4 results in C2H6 and C2H4 (C2 compounds), and the combined C2 yields follow the same order with Dy203 » Ce02. The MIESR and flow reactor results are in qualitative agreement, with the exception of Nd203.