An ab initio investigation of the energy barriers for hydrogen reduction of CuCl on copper(111) surfaces, as well as in the; gas phase, has been performed in the present investigation. it is concluded that the elimination of chlorine from CuCl by the addition of H-2 proceeds via surface reactions between hydrogen and CuCl both adsorbed on Cu(111), The activation energy for the reaction between CuCl (adsorbed on a threefold site) and ii (adsorbed on an adjacent on;cop site) is only 53 kJ mol(-1), i.e., almost identical to the reaction energy for this surface process. However, the CuCl + H surface reaction should presumably start with both species adsorbed in their preferred threefold sites. By assuming that H diffusion from threefold to top is not hindered by any barrier, the barrier energy for the most possible surface reaction is estimated to become 83 kJ mol(-1). This value is in close correspondence to the experimental value of 85 kJ mol(-1) that has been previously reported.