To probe into the expression of alpha subunit for IL-6R at both mRNA and protein levels in human leukemic cells and to discuss its implication in targeted treatment for leukemia with recombinant IL-6-PE40 exotoxin fusion protein mediated by IL-6/IL-6R system, semi-quantitative RT-PCR, sequencing and FCM were used to analyze the gene and protein expression levels of alpha subunit for IL-6R in leukemic cells. Our results showed that not only mRNA but also protein of alpha subunit for IL-6R are highly expressed in the myelogenous leukemic cell lines, the relative expression levels of mRNA were KG-1(1.22) > (1.02) > U266(1.00) > U937(0.99) > HL-60(0.76). Among lymphoblastic leukemic cell lines, Raji expressed a certain amount of alpha subunit mRNA (0.77), whereas its alpha subunit protein was not detected. Expression of alpha subunit mRNA and protein were negative in lymphoblastic leukemic cell lines, HuT28 and CEM, and chronic myelocytic leukemic cell line K562. These results correlate with those of FCM highly. Noteworthily, normal human peripheral blood mononuclear cells expressed hardly protein of IL-6R alpha subunit. So this study provides sufficient experimental evidence that the targeted treatment by recombinant IL-6-PE40 can specifically kill leukemic cells highly expressing IL-6R without toxicity to normal hematopoietic cells.