Objective To evaluate the relationship between WT1 gene expression and leukemia, as well as its significance. Methods Expression of WT1 gene was measured with RT-PCR in 68 cases of leukemia at different disease-developing stage. Results Expression of WT1 gene was revealed in 65%newly diagnosed and relapsed acute leukemia and 44%chronic myelogenous leukemia (CML). All of 4 patients with CML at blast crisis stage had positive expresion of WT1. As contrast, neither 10 volunteers, nor 10 patients with no-hematological disease were WT1 positive. Conclusion Expression of WT1 gene was revealed in all kinds of leukemia patients and associated with quantity of leukemic cells. RT-PCR was so far the most sensitive method for minimum residual disease (MRD) detection after chemotherapy and bone marrow transplantation. And it was also useful in pathogenesis study and prognotic evaluation in leukemia.