Anaemia was induced in rats with fluorouracil (5-FU) or cisplatin (CDDP) and the mechanisms of anaemia induction were analysed. Furthermore, the therapeutic effects of recombinant human erythropoietin (rHu Epo) on these anticancer drug-induced anaemias were investigated. In 5-FU-induced anaemia, marked serum erythropoietin (Epo) elevation was observed in inverse correlation to blood Hb concentration and Hb concentration rapidly recovered to normal levels. On the other hand, in CDDP-induced anaemia, serum Epo elevation was modest and the lowered Hb concentration persisted longer. Treatment with rHu Epo significantly improved both anticancer drug-induced anaemias but rHu Epo was more effective on CDDP-induced anaemia. These results suggest that rHu Epo might be useful for the therapy of anaemia associated with anticancer chemotherapy.