The photoyellowing of papers produced from bleached CTMP is retarded when these papers are irradiated in aqueous solutions containing reducing agents such as Rongalit C and Blankit D. Papers impregnated with the reducing agents showed some photostability when irradiated in the dry state but not when irradiated in aqueous solution. The reducing agents present in these papers also failed to significantly retard the photoyellowing under natural lighting conditions and under simulated solar irradiation. It is concluded that the migratability of the reducing agents is important if photoprotection is to be achieved and that the latter is caused by the reagents bleaching the yellow photodegradation products as well as destroying prodegradent species such as hydroperoxides.