The kinetics of enzymatic oxidative polymerization of 4-chloroguaiacol by laccase was studied. 4-Chloroguaiacol, a model compound of the chloroguaiacols formed in the bleaching process in the pulp industry, was oxidized by laccase from Trametes sp. Ha1 to eliminate chloroguaiacols from pulp wastewater by polymerization and precipitation. On the basis of the reaction rate obtained from the decrease in the 4-chloroguaiacol concentration, the optimum pH of the reaction was 4-5 and the apparent Michaelis constant K. for the reaction was more than 5 mmol dm(-3). However, the value of K. obtained from the dependence of oxygen consumption rate on the concentration of 4-chloroguaiacol was 0.092 mmol dm(-3). The reaction rate was expressed as the sum of the enzymatic oxidation rate of 4-chloroguaiacol and the polymerization rate of the radical formed in the enzymatic oxidation. The kinetics of the enzymatic oxidative polymerization shown in this study will be useful to understand those of the enzymatic oxidation of other phenolic compounds.