This study was purpose to investigate the expression levels of HSP70 and MDR1 genes under heat shock and/or adriamycin (ADM) chemotherapy stimulation. The K562 cells were bathed in water at 43 degrees C for 1 hour, then the heat-treated K562 cells were collected and were cultured at 37 degrees C. The expression of HSP70 was assayed by immunocytochemistry, the growth suppression rate of K562 cells was detected by MTT assay, the function of P-gp and the expressions of HSP70 mRNA, MDR1 mRNA were detected by flow cytometry and real-time quantitative PCR (RT-PCR) respectively. The results showed that (1) the synthesis of HSP70 protein in K562 cells treated with high shock (43 degrees C) reached to high level after culture at 37 degrees C for 2 hours, and moved from cytoplasm to nucleolus, the expression of HSP70 began to decrease following 3 hours of culture at 37 degrees C, and gradually reached to normal level after culture at 37 degrees C for 5 hours, the location of HSP70 expression returned to cytoplasm; (2) the expressions of HSP70 mRNA and MDR1 mRNA increased following 43 degrees C heat shock, and were 4 and 5.8 times higher than that of control group at 37 degrees C culture for 2 hours respectively; (3) the expression of P-gp was higher in ADM group than that in control. The expressions of HSP mRNA and MDR1 mRNA increased significantly in heat shock plus ADM group and ADM group as compared with control (p<0.01). It is concluded that the heat shock and ADM chemotherapy both induce over expression of HSP70 and MDR1 which can maintain stability of K562 cells and may be related to formation of the MDR in leukemia.