Kinetics of the adduct formation of cisplatin and its hydrolysis products with 5'-GMP was investigated using capillary electrophoresis (CE) under 'simulated physiological conditions'. Therefore, chloride ion and phosphate concentration as well as the pH were chosen comparable to intracellular conditions. Furthermore, the influence of the sulfur-containing alpha-amino acids L-methionine and L-cysteine on the kinetics of the adduct formation have been studied. Both amino acids increased the half-time of the reaction significantly but did not influence the formation of the major adduct cis-[Pt(NH3)2(N7-GMP)2]2-. The reaction products were separated using CE, and characterised using UV and NMR spectroscopy.