The kinetics of carboxymethylation of mercerized Na-cellulose was studied in a laboratory-scale batch reactor operating at atmospheric pressure and at temperatures in the range 30-80-degrees-C. Based on the experimental data a bimolecular kinetic model for carboxymethylation was developed. The model takes into account the decline of the intrinsic activities of the hydroxyl groups of cellulose as the substitution proceeds. The parameters of the kinetic model were determined by regression analysis, and the model described well the experimentally determined carboxymethylation kinetics. The distribution of mono-, di-, and trisubstituted anhydroglucose units in (carboxymethyl)cellulose was simulated using the parameters of the kinetic model.