The influence of X-irradiation on leakage currents in SiOx(CH3)gamma-based dielectric films has been studied. In both unirradiated and irradiated samples, the natural logarithm of the leakage current density (J) varies as the (applied electric field)(1/2) at high electric fields consistent with the bulk-limited Poole-Frenkel mechanism although the measured slope of the curve is smaller than expected by a factor of 1.5. Radiation induces a shift of the ln(J) vs. E-1/2 to lower voltages in samples exposed in the presence of zero and 1.5 MV cm(-1) bias indicating significant charge trapping. We find clear evidence for uptake of moisture in the films leading to enhanced conductivity. (C) 2003 The Electrochemical Society.