The oxidative coupling of methane over Mn/Na2WO4/SiO2, Mn/Na2WO4/MgO, and NaMnO4/MgO catalysts was studied using both a cofeed flow system and a pulse reactor. At 800 degrees C and 1 atm, and using a CH4/O-2 ratio of ca. 8/1, a methane conversion of 20% was achieved at a C-2+ selectivity of greater than or equal to 80%, with no diluent in the reagents. The similar catalytic behaviors of the three catalysts suggest that a common active site, consisting of an Na-O-Mn species, may be involved. Results from a pulse reaction sequence (an O-2 pulse followed by a series of pure CH4 pulses) indicate that the active species are not stable under reaction conditions unless gas phase O-2 is present, and that bulk lattice oxygen does not participate in the methane coupling reaction when carried out in the cofeed mode. There is a linear relationship between the specific activity for CH4 conversion and the concentration of surface Mn, which is believed to be responsible for the activation of O-2. The resulting form of oxygen then abstracts a hydrogen atom from CH4. Sodium is essential for preventing the complete oxidation of CH4, perhaps by isolating the Mn ions. The tungstate ions appear to impart stability to the catalysts.