We study the effect of intense laser radiation on the surface of silicate glass prior irradiated by gamma radiation. Experimental results show that the gamma radiation with dose 5 × 10⁴ R leads to the degradation of the surface resistance of this optical dielectric to electromagnetic radiation. Depending on the dose of the radiation the laser radiation can result in either surface erosion or its pronounced cracking. It is also found that the efficiency of the degradation process is determined not only by the radiation dose, but also by the presence of different impurities in the glass.