Many pharmaceutical compounds and metabolites are being found in surface and ground waters, indicating their ineffective removal by conventional wastewater treatment technologies. Advanced oxidation processes for the transformation of 6-aminopenicillanic acid in water are alternatives to traditional water treatment. Therefore the kinetics of oxidation of 6-aminopenicillanic acid by diperiodatoargentate(III) in alkaline medium at a constant ionic strength of 0.04 mol dm(-3) was studied spectrophotometrically at 25 degrees C. The oxidation products, 2-formyl-5,5-dimethylthiazolidine-4-carboxylic acid and Ag(I), were identified by LC-ESI-MS and IR spectral studies. The reaction between 6-aminopenicillanic acid and diperiodatoargentate(1111) in alkaline medium exhibits I: I stoichiometry. The reaction shows first order with respect to diperiodatoargentate(III) concentration. The order with respect to 6-aminopenicillanic acid and alkali concentrations is less than unity. The rate goes on decreasing with the increase in the concentration of periodate. Monoperiodatoargentate(III) is considered the active species of the diperiodatoargentate(111). A possible mechanism is proposed. The reaction constants involved in the different steps of the mechanisms are determined. The activation parameters with respect to the slow step of the mechanism are calculated and discussed. The thermodynamic quantities are also determined.