Luminescence spectra of pure AgBr have been investigated in the vicinity of the indirect band gap at the temperature region between 500 mK and 50 K by using 3 He-coolant under various excitation conditions. Systematic studies of the effects of annealing on luminescence spectra of free excitons in AgBr have revealed that the lifetime of free excitons in a specimen after annealing can be extremely prolonged and the excitonic temperature in the specimen can be further lowered than that in a specimen before annealing. Luminescence spectra for an annealed specimen under a uniaxial stress at low temperatures have also been studied to ensure an understanding of the cause of these two phenomena.