The mechanism of the partial oxidation of methane to synthesis gas over the Ru/TiO2(Ca2+) catalyst is investigated employing non-steady-state and steady-state isotopic transient experiments, combined with in situ DRIFT spectroscopy. The main objective is to identify the active intermediate species involved in surface transformations and the mechanistic reaction pathways. It was found that gas-phase CH4 interacts with the catalyst surface, producing CH., surface species. This process is irreversible and is characterized by a slow rate. CHx species are fully dehydrogenated toward surface carbon. Adjacent metallic Ru sites as well as atomically adsorbed oxygen participate in the process of hydrogen abstraction from CHx, species. The primary product of the reaction is CO, which results from the surface reaction between carbon and adsorbed atomic oxygen on metallic Ru sites, while CO2 derives from CO oxidation on oxidized sites. The unique ability of the Ru/TiO2 catalyst to promote the direct formation of H-2 and CO is attributed to its high resistance to oxidation under conditions of partial oxidation of methane.