The aim of the present study was to investigate the influence of different stages of leukemia P388 on the pharmacokinetics of the antineoplastic agent mitoguazone in mice. It could be shown that, independent of the tumor stage investigated, the total clearance of mitoguazone is slightly reduced reflecting a moderate increase of AUC in the serum of leukemia-bearing animals. Furthermore, in an advanced tumor stage the drug levels in kidneys, liver, spleen and serum were found to be elevated to some extent in comparison to tumor-free controls in contrast to an earlier stage of leukemia. In conclusion, the tumor stage has to be considered as an important factor to which extent a neoplasia may alter the pharmacokinetics of drugs used for anticancer chemotherapy.