The kinetics of the reaction between a dichlorotriazine reactive dye and methanol was studied in supercritical carbon dioxide and in a solution of pure methanol. The experiments were carried out in a batch reactor at different temperatures between 333 and 393 K and at 300 bar when supercritical carbon dioxide was the solvent medium. The rate constants and the parameters of the Arrhenius equation were determined and compared. A significant influence of the supercritical carbon dioxide on the rate constants was found. The formation of methoxy-dye was faster over the whole temperature range in pure methanol than in supercritical carbon dioxide. But the consecutive reaction, the formation of dimethoxy-dye, was considerably faster, up to 20 times, in supercritical carbon dioxide than in pure methanol. Moreover, the lowest value for the activation energy, 50 +/- 13 kj mol(-1), was found for the consecutive reaction in supercritical carbon dioxide. In this paper new kinetic data for the methanolysis reaction of a dichlorotriazine reactive dye in supercritical carbon dioxide are shown. (C) 2004 Elsevier B.V. All rights reserved.