The CH4 direct oxidation reaction was studied at 600 degrees C by the pulse-MS transient method over the Ni/La2O3 catalyst. Over the freshly prepared catalyst (which contains NiO), the CO selectivity and CH4 conversion increased and attained constant values as the number of CH4/O-2 pulses increased. Over the reduced catalyst (containing Ni), as the number of CH4/O-2 pulses increased, the CO selectivity and CH4 conversion decreased before they reached the same constant values as over the fresh catalyst. The CO selectivity increased as the residence time of the reactants shortened, implying that CO was directly generated without the preformation of CO2. The activation energies of CH4 dehydrogenation in the presence and absence of oxygen have been calculated using the bond-order conservation Morse-potential approach. The results indicate (1) the direct dehydrogenation steps are more likely to occur; (2) the transient oxygen species adsorbed on-top of the metal atoms promote dehydrogenation; (3) the oxygen species adsorbed on bridge or hollow sites do not promote dehydrogenation.