The effects of gamma-ray irradiation on the dielectric properties of Au/SiO2/n-Si (MIS) structures were investigated. Structures were exposed to a Co-60 gamma-radiation source with a dose rate of 2.12 kGy/h. The dielectric constant (epsilon'), dielectric loss (epsilon ''), loss factor (tan delta) and ac electrical conductivity (sigma(ac)) were calculated from the C-V, and G/omega-V measurements and plotted as a function of radiation dose at high frequency (1 MHz). A decrease in the epsilon' and epsilon '' was observed as the irradiation dose was increased. The decrease in the magnitudes of the c and c of irradiated MIS structures is explained on the basis of Maxwell-Wagner interfacial polarization. The obtained data from the C-V and G/w-V measurements suggest that these structures may be used in radiation dosimetry applications.