Low-held leakage currents in thin gate oxides can be induced by 10 keV x-ray irradiation and electrical stress. The characteristics of radiation-induced leakage current (RILC) and stress-induced leakage current (SILC) in thin oxides have been studied and compared. The characteristics of RILC are found to be very similar to SILC, indicating that both RILC and SILC have essentially the same conduction mechanism, and are contributed by common defects generated in the gate oxides during irradiation or electrical stress. in particular, it has been demonstrated that oxide-trapped holes contribute significantly to both RILC and SILC.