Physical and chemical effects on a cellulose paper (80% cotton, bleached chemical pulp) of sodium hypochlorite at pH 2.5, and of a chlorine dioxide solution made by mixing sodium chlorite and formaldehyde. Measurements were made immediately after treatment, during the course of a 12-day dry aging at 105°, and additionally after a 23-year storage at room temperature. Neither reagent can be recommended for paper bleaching. The poorest results were obtained with acidified hypochlorite. Therefore, known alternative treatments are advised. General criteria for this kind of treatment, and the possible oxidative modifications of cellulose are also discussed.