The kinetics of ruthenium(III) catalysed oxidation of atenolol by diperiodatonickelate( IV) (DPN) in alkaline medium at a constant ionic strength of 1.0 mol dm(-3) has been studied spectrophotometrically using a rapid kinetic accessory. The reaction exhibits 1:1 stoichiometry (DPN: atenolol). The reaction shows first order dependence on [DPN] and [Ruthenium( III)] and apparent less than unit order dependence each in atenolol and alkali concentrations. Addition of periodate has no effect on the rate of reaction. Effect of added products, ionic strength and dielectric constant of the reaction medium have been investigated. The main products were identified by IR, NMR, fluorimetry and mass spectral studies. The results suggest the formation of a complex between the atenolol and ruthenium(III) species which reacts with one mole of diperiodatonickelate(IV) species in a rate determining step, resulting in the formation of a free radical, which in a subsequent fast step yields the products. The reaction constants involved in the mechanism were evaluated. The activation parameters were computed with respect to the slow step of the mechanism and discussed.