Reduction and decomposition of nitric oxide using methane as a reducing agent has been studied in the presence and absence of oxygen over Pd/TiO2 catalysts. Temperature-programmed adsorption/desorption and reduction/oxidation behavior has been examined. Prereduced catalysts have shown significant reduction as well as decomposition activity. Isotopic labelling studies using (CH4)-C-13, (NO)-N-15-O-18, (NO)-N-15, and O-18(2) have also been performed to investigate the interaction of NO and methane with the catalytic sites.