The effects of chitosans on hydrogen peroxide decomposition were studied under alkaline conditions by determining the resid- ual hydrogen peroxide content after the addition of chitosans and metals in the absence of pulp. As shown in Fig. 3, three metals could accelerate the decomposition of hydrogen peroxide, and their ability to catalyze the hydrogen peroxide decomposition ranked as follows: Mn> Cu > Fe. Manganese has been considered to most strongly induce hydrogen peroxide decomposition (Lapierre, Bouchard, & Berry, 1995). The addition of chitosans could inhibit the hydrogen peroxide decomposition catalyzed by various transi- tion metals. The performance of chitosans depended on the types of metals used. Chitosans with DD of 85% and 95% could both inhibit the decomposition of hydrogen peroxide in the presence of cop- per. A higher dosage of chitosans (0.5%) more efficiently inhibited the decomposition of hydrogen peroxide than did a lower chitosan dosage (0.25%). The chitosan with a DD of 95% inhibited the decom- position of hydrogen peroxide better than did the chitosan with a DD of 85%.