The photochemical activation of methane over a substrate containing Rh-I(CO)(2) species has been studied using transmission infrared spectroscopy. At 233 K, methane activation is achieved by the oxidative addition of the C-H bond to a postulated 16-electron surface species, Rh-I(CO), which is produced by UV (325 nm) photodecomposition of the Rh-I(CO)(2) on the surface. The oxidative addition product, Rh(CO)(H)(CH3), further undergoes a migratory-insertion reaction in the presence of CO to form a proposed Rh(CO)(H)(COCH3) surface species. Isotopic experiments using (CO)-O-18 have been performed to confirm the product assignment. An IR spectroscopic study of acetaldehyde and acetone adsorption following the photoreaction suggests that other CH3CO-containing species may also be formed on the surface as a result of C-H bond activation followed by CH3 insertion into the Rh-CO bond region.