Abstract— This paper is a critical review of the singlet oxygen oxidation of polymers in solid state and in solution, referring in particular to polydienes, polystyrene and polyvinyl chloride). The singlet oxygenation of polydienes resulted in formation of allylic hydroperoxide groups with shifted double bonds, according to the “ene”-type process. The singlet oxygenation of polystyrene and polyvinyl chloride) occurs only when the new double bonds are formed in these polymers. During dye-photosensitized singlet oxygenation of polydienes in methanol-benzene solution, a very rapid decrease in the molecular weight was observed. For the chain-scission which occurs, not only singlet oxygen but several intermediates such as radicals, bi-radicals and cation-radicals which are formed during light fading of dyes are responsible. At the end of this paper a short review appears which has been focused on the quenching behavior of stabilizers, particularly interactions with singlet oxygen.