Thermal bleaching of silver halide photochromic glasses is studied by electron paramagnetic resonance spectroscopy of photoinduced CuII centers. During exposure to ultraviolet light, the only stable CuII species is the (CuIIVAg)A center, 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  direction, with an activation energy E3=0.44 eV and a frequency factor k30=3.4×105 s-1. The second channel involves the conversion of the (CuIIVAg)A center into a (CuIICl-VAg)B center, where the silver vacancy is in the next nearest position along the  direction. This process occurs with an activation energy E1=0.44 eV and a frequency factor k10=3.1×105 s-1. The (CuIICl-VAg)B center slowly decays by a vacancy hopping mechanism, with an activation energy E2=0.22 eV and a frequency factor k20=4.6 s-1. To explain these two decay channels, it is proposed that the (CuIIVAg)A and (CuIICl-VAg)B centers annihilate via the formation of a CuI ion and a neutral complex (AgIIVAg)A which migrates to the surface of the silver halide particle, where electron‐hole recombination occurs.