Thermal gas-release characteristics of copper single-crystal specimens bombarded by a high-energy Xe+ ion beam are presented. The influence of the crystallographic orientation of the targets bombarded, of the ion energy, and of the total ion dose was investigated. The ion energy ranged from 20 to 80 keV, and the total ion dose from 1013 to 1018 ions/cm2. Curves for fractional gas release were obtained by the method of stepwise thermal treatment, using the radioactive tracer technique. From the experimental data obtained and the theoretical expectations, corresponding activation energies for gas release were deduced. Thermal stability of the gas embedded in the target is discussed.