The acid-catalyzed oxidation of kappa-carrageenan (KCAR) polysaccharide as a natural polymer by chromic acid in aqueous perchloric acid at a constant ionic strength of 4.0 mol dm(-3) have been investigated spectrophotometrically. A first-order reaction in chromic acid and a fractional-order with respect to KCAR concentrations were revealed. A kinetic evidence for the formation of 1:2 complex between chromic acid and KCAR is presented. The influence of hydrogen ion concentrations on the reaction rates showed that the oxidation process is acid-catalyzed. The kinetic parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results is discussed. (C) 2008 Elsevier B.V. All rights reserved.