Methyl radicals, produced by the high temperature pyrolysis of azomethane, were adsorbed on Rh/SiO2. The reaction between adsorbed CH3 and gaseous CO2 has been followed by determining the intensity changes of the asymmetric stretch of CH3 and the composition of the gas phase. It was found that adsorbed CH3 reacts with CO2 at and above 373 K. It is assumed that similar processes may also take place in the dry reforming of methane, and that they are responsible for the lack of carbon deposition on sup ported Rh catalysts.