The kinetics of ruthenium(III)-catalysed oxidation of reducing sugars, viz. glucose, fructose, galactose, lactose and maltose, by sodium metaperiodate has been investigated. The following rate law is observed on the basis of kinetic results where However, the first order dependence of the rate with respect to each, i.e. substrate and oxidant at lower concentrations have been observed: the decrease in the observed rate constant (Kobs) with an increase and a decrease in the order of reaction with respect to and substrate at higher and substrate], respectively. The kinetic data support the formation of 1:1 complex between . Formaldehyde has been observed as the major product of reducing sugar under the kinetic condition and a mechanism consistent with kinetic data has been proposed and discussed.