To study an association between iron metabolism, free radical oxidation (FRO), and antioxidative system (AOS) in patients with acute myeloid leukemia (AML) during intensive chemotherapy. AML patients (n = 14) with a median age of 46 years received 7+3 courses (n = 3) containing cytarabine > or = 1 g/m2/introduction (n = 8) and myeloablative conditioning regimen before hematopoietic stem cell transplantation (n = 3). The concentrations of iron, ferritin, transferrin saturation (TFS), and malonic dialdehyde and the activity of superoxide dismutase (SOD), ceruloplasmin (CP), and catalase were investigated in their sera. The investigations were performed before and after chemotherapy and during hemopoietic recovery and rehospitalization. RESULTS; After therapy termination, there was a significant increase in TFS (6.8% vs 41.9%; p < 0.0001), which gave way to its reduction during hemopoietic recovery (89.5% vs 96.8%; p = 0.003). The activity of antioxidant enzymes was found to be altered at a time. That of catalase was enhanced throughout cytopenia (3.8 and 3.3 vs 5.7 conventional units (CU)/ml; p = 0.028 and p = 0.011). The lower activity of SOD (21.0 vs 41.0 CU/ml; p = 0.018) and the higher activity of CP (1.1 vs 0.8 g/l) were ascertained when leukocyte count increased up to > or = 1 x 10(9)/l. After intensive cytostatic therapy, there was a phasic TFS increase accompanied by the compensatory change in AOS activity, which is aimed at neutralizing FRO products.