Thermal bleaching of silver halide photochromic glasses is studied by electron paramagnetic resonance spectroscopy of photoinduced CuIIcenters. During exposure to ultraviolet light, the only stable CuIIspecies is the (CuIIVAg)Acenter, which is a CuII‐silver vacancy complex with the vacancy in a nearest position. In the dark, this center rapidly decays via two parallel channels. The first involves the dissociation of the complex by displacement of the vacancy along a [110] direction, with an activation energyE3=0.44 eV and a frequency factork30=3.4×105s−1. The second channel involves the conversion of the (CuIIVAg)Acenter into a (CuIICl−VAg)Bcenter, where the silver vacancy is in the next nearest position along the [100] direction. This process occurs with an activation energyE1=0.44 eV and a frequency factork10=3.1×105s−1. The (CuIICl−VAg)Bcenter slowly decays by a vacancy hopping mechanism, with an activation energyE2=0.22 eV and a frequency factork20=4.6 s−1. To explain these two decay channels, it is proposed that the (CuIIVAg)Aand (CuIICl−VAg)Bcenters annihilate via the formation of a CuIion and a neutral complex (AgIIVAg)Awhich migrates to the surface of the silver halide particle, where electron‐hole recombination occurs.