The heterogeneous oxidative polymerization kinetics of 2,6-dimethylphenol (DMP) catalyzed by a copper(II)-EDTA complex in water was studied. During the oxidative polymerization of DMP in water the oxygen uptake rate increases with an increase in DMP concentration and an increase in temperature. The Michaelis-Menten kinetic model as applied to the polymerization of DMP in organic solvents is not appropriate for the description of the full course of DMP polymerization in water. A new heterogeneous kinetic model is proposed to describe the catalyst deactivation during the oxidative polymerization as well as the difference in reactivity between the monomer, water-soluble oligomer and water-insoluble oligomer. The polymerization rate estimated by the new model is consistent with the measured data. (C) 2009 American Institute of Chemical Engineers AIChE J, 55: 2716-2724, 2009