Adsorption properties and activity of cobalt and nickel catalysts have been studied by temperature programmed desorption （TPD） of carbon monoxide and by methanation test, as the catalysts are contaminated by surface carbon and are regenerated by hydrogen treatment thereafter. Carbon on the catalyst surface has been accumulated by disproportionation of carbon monoxide at elevated temperatures. It has been observed that catalysts with surface carbon deposited at 450 ℃ are deactivated more rapidly than those with carbon deposited at 300 ℃, and also that the former are more easily regenerated by hydrogen treatment than the latter. Cobalt undergoes more severe deactivation than nickel by surface carbon accumulation, but it is readily regenerated by hydrogen treatment. In this study, catalyst deactivation by surface carbon could be monitored by changes in the TPD chromatogram, which showed reduction of peaks below 200 ℃ accompanied by a new peak appearing above 300 ℃. However, the catalyst rege neration process could not be monitored in this manner, which may suggest that the structure of the catalyst has been modified during the deactivation and regeneration processes.