AIM:To establish a real-time PCR technique for detection and quantification of TCR ? chain expression and to investigate TCR ? chain expression level in patients with chronic myeloid leukemia(CML).METHODS:Real-time PCR with SYBR GreenⅠ technology was used for detecting TCR ? chain expression level in peripheral blood mononuclear cells from 30 patients with CML and 30 normal individuals.?2-microglobulin gene(?2M) was used as an endogenous reference.Relative changes in TCR ? chain expression level were used by the 2-Ct method between patients with CML and normal individuals.RESULTS:The SYBR GreenⅠ real-time technique for quantitative detection of TCR ? chain expression levels was established successfully.The expression level of TCR ? chain in 18 patients with CML was reduced.However,the TCR ? chain expressed increased in 12 patients with CML.CONCLUSION:The TCR ? chain expression level is divided into down expression(60%) and over expression(40%) groups,and the down expression of TCR ? chain might related to cellular immunodeficiency in most of CML patients.