The absorption spectra of unirradiated and irradiated (to fast neutron fluence 1012 and1014 cm-2 in VVR-SM) quartz-quartz fibers after additional irradiation with 60Co γ rays to 108 rad are investigated. It is shown that neutrons transform E centers into Si-Si centers. The kinetics of accumulation of bridge oxygen atoms under the action of γ radiation exhibits two stages. The first stage is due to neutron irradiation and the manifestation of preliminary potential centers of nonbridge oxygen atoms. The second stage is associated with the creation of additional nonbridge oxygen atoms under the action of γ radiation. The γ-ray dose for the onset of the second stage decreases as the fluence of the preliminary neutron irradiation increases.