The thermoluminescence of X-ray coloured NaCl and NaCl:Cu crystals is studied in the temperature range 300 K-510 K. Five glow peaks centred at 343, 363, 391, 420 and 445 K are recorded for a warming rate of 40 K min^-1 and analysis indicates first order kinetics with activation energies 1.05, 1.12, 1.21, 1.47 and 1.47 eV respectively. The 391 and 420 K peaks can be related to the presence of dissolved copper ions. The first (391 K) is ascribed to hole release from Cu²⁺ centres formed by irradiation while electron release from an F centre neighbouring a Cu²⁺ ion is believed to cause the 420 K peak. It is suggested that the other peaks originate from F centres generated during the initial growth stages.