A method for determination of cis-diaminedichloroplatinum (II) (cisplatin) in ultrafiltered plasma, cell, and tumour samples is described. Cisplatin separation was carried out on a reversed-phase column using methanol-acetonitrile-water as the mobile phase. The flow rate was maintained constant at 1.6 mL/min and analysis was performed at 23 degrees C. Detection was carried out by absorbance at 254 nm. The method was linear in the range of 0.2-10 microg/mL, and the coefficients of variation were <10%. Using this technique, we measured the intracellular accumulation of cisplatin in cancer cells and in tumours of mice receiving treatment with cisplatin and evaluated the pharmacokinetics of cisplatin in nu/nu mice after intraperitoneal (i.p.) administration. The method proved to be adequate for measuring cisplatin both in vitro and in vivo and could be suitable for studies of cisplatin pharmacokinetics in animal models.