The kinetics and mechanism of reduction of hexacyanoferrate (III) by biodegradable chondroitin-4-sulfate (CS) in alkaline solutions at a constant ionic strength of 1.0moldm−3 have been investigated spectrophotometrically. The kinetic results indicated that the reaction was first-order dependence in the oxidant and fractional-order kinetics with respect to the [CS]. The influence of the base on the oxidation rates indicates that the reaction was base-catalyzed. A kinetic evidence for formation of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results obtained is suggested and discussed.