The kinetics of the alternating copolymerization of ethylene with carbon monoxide has been studied in the presence of a palladium catalyst immolized on a polymer support in various media (methanol, toluene, heptane). In the case of hydrocarbon solvents, the activity of the supported catalyst is commensurable with the activity of a homogeneous system in methanol. The melting temperature of the resulting copolymer and its molecular mass depend on the solvent nature. The IR reflectance spectra of the active palladium complex and the ethylene-carbon monoxide copolymer are measured.