Anemia is the major stimulus for erythropoietin (Epo) secretion. Various studies have reported increase of Epo following chemotherapy. The mechanism of this phenomenon is not yet clarified. In this study, the serum Epo levels have been evaluated before, during (7 and 14 days), and after (day 25) chemotherapy in patients with acute myeloblastic leukemia (n = 13) and lymphoblastic leukemia (n = 4). As a control group. 12 healthy age-matched subjects were evaluated. Epo levels were high in untreated leukemia patients compared to controls and continued Lo increase following chemotherapy. There was no significant difference in post-treatment values of Epo as compared with pre-treatment levels. In patients with pre-treatment values of Hb less than or equal to 9 g/dl, Epo levels were inversely correlated with Hb (r = 0.552; p < 0.05). This correlation disappeared during and following treatment. There was no correlation between Epo levels and hematological or biochemical parameters. Therefore, elevated levels of Epo regardless of anemia may be due to a response to tissue hypoxia or increased synthesis of Epo in liver or bone marrow.