HPLC with DAD (diode array detector) was applied as rapid method for the analytical control of the purity and stability of carboplatin and oxocarboplatin as effective cytostatics of 2nd generation. The stability of carboplatin has been measured in some infusion media (sodium chloride, glucose, sodium citrate) and compared to the cisplatin (cytostatic of 1st generation) stability. In addition ligand-exchange reactions between cisplatin and carboplatin have been studied together with the influence of temperature, pH and the concentrations of reactants. A method was developed for the analysis of clinical samples using solid-phase extraction as a preseparation and preconcentration step. The detection limits were 5 μg/ml serum for cisplatin, 0.16 μg/ml for carboplatin and 0.23 μg/ml for oxo-carboplatin.