Abstract: The distribution of TCR Vβsubfamilies T cells was analyzed using RT - PCR,which amplified the Complementarity determining region 3(CDR3)of TCR Vβgene inperipheral blood mononuclear cell(PBMC) with chronic myeloid leukemia(CML), 8cases normal samples and T cell line K37 serve as control. The PCR Products were further studied by genescan analysis to identify tO the T cell clonality. The expression of 3-21Vβ subfamilies was found in PBMC from 12CML cases, besides Vβ20, all subfamilyT cells of TCR Vβwere identified in PBMC of 8 control cases, but only one Vβsubfamily(Vβ)was expressed in T cell line K37. The genescan analysis showed that some Vβsubfamily products from 8 of 12 CML cases contained a dominant peak. The result indicatedthat T cell clonality expansion may be found in CML cases. Suggesting that may indicatea host response directed against leukemia cell related antigen. This analysis method maybe useful as a new molecular biologic analysis tool for clinical study of specific immunetherapy in leukemia.