The paper presents experimental results on an in situ optical absorption study of the reduction/oxidation processes in YAlO(3):Mn crystals that are visible in the [Formula: see text] recharging of manganese ions. The appearance of the Mn(5+) absorption during annealing in an oxidizing atmosphere as well as its bleaching during annealing of the crystal in a reducing atmosphere have been studied in the temperature range from 800 to 1250 K. The oxidation and reduction kinetics are analyzed in the framework of the vacancies diffusion model and compared with the nominally pure and Nd-doped YAlO(3) crystals studied previously.