This study was aimed to detect the expression of B7-H1 gene in the acute myeloid leukemia (AML) cells and to explore its clinical significance. The B7-H1 gene expression was detected by real-time quantitative PCR in bone marrow mononuclear cells (BMMNC) from 40 newly diagnosed AML patients, 10 normal volunteers and 10 relapsed patients. The results showed that the expression of B7-H1 from de novo AML patients was lower than that from the normal volunteers, but it was higher in the relapsed patients. The expression level of B7-H1 gene before therapy was significantly higher in non CR patients than that in CR patients after therapy. It is concluded that there is a correlation between the expression level of B7-H1 gene and response to therapy.