Chlorine adsorption on Cu(111) has been studied at low temperatures using LEED and AES. AT 165 K a (6 square root 3*3*6 square root 3)R30 degrees chemisorbed structure was formed at saturation. At 110 K adsorption continued, forming multilayers of copper chloride with the (6 square root 3*6 square root 3)R30 degrees structure still intact at the interface between the chloride and the copper. Electron-stimulated desorption was observed from the (6 square root 3*6 square root 3)R30 degrees structure at 165 K but not at 300 K, which is consistent with a high surface mobility for chemisorbed chlorine.