UV-induced coloration and decreasing of the fast component's intensity of UV-excited luminescence in unirradiated silica glasses and UV-bleaching and decreasing of the fast component's intensity of the luminescence in gamma- irradiated silica glasses have been studied. In the experiments, unirradiated and irradiated by the gamma-ray dose 105 rad in 1987 high purity multicomponent silica glasses and N2-laser ((lambda) equals337 nm, (tau) approximately equal to 9 ns, repetition frequency 40 Hz, P approximately 6 MW/cm2) were used. The glasses had 5-6 eV band gap and less than 10-5 wt.% impurity concentration. During 20 min of laser irradiation the absorption coefficient of the unirradiated glasses at 337 nm is increased by 0,25 cm-1 and luminescence intensity was decreased by 35-40%. In gamma-irradiated silica glasses UV-irradiation leads to bleaching of gamma-induced coloration and decreasing of the intensity of UV-irradiation excited luminescence. After laser irradiation of the gamma- irradiated glasses during 20 min, their absorption coefficient at 337 nm is decreased by 0,13 cm-1 and the fast component's intensity is decreased by 30-40%. It should be pointed out, that both unirradiated and gamma- irradiated samples of glasses have the luminescence intensities of an equal value, but the absorption coefficients are different. These effects and luminescence time resolved spectra depend on the UV-irradiation intensity and are explained by the two photon absorption of laser irradiation in glasses.