Annealing o inter ace defects in metal-oxide-semiconductor (MOS) devices by x-ray irradiation has been observed. The effect occurs in rad-hard devices which had been previously damaged severely by high-field Fowler-Nordheim electron injection, but has not been observed in standard MOS devices which are not radiation-hardened. A mechanism based on the recombination-enhanced-defect-reactions process is proposed to explain the results.