Background In general,it is very important to understand the state of T cell immune response against tumor cells in leukemia patients and it is especially critical to assess the T cell repertoire of untreated patients. As we know,few studies have dealt with the distribution of oligoclonal T cells in leukemia,so we investigated the distribution and clonality of TCR Vβ repertoire of T cells in patients with chronic myelogenous leukemia (CML) in chronic phase. Methods The complementarity determining region 3 (CDR3) of TCR Vβ24 subfamily genes were amplified in peripheral blood mononuclear cells from 27 cases with CML using reverse transcription-polymerase chain reaction (RT-PCR). In order to observe the distribution of TCR Vβ repertoire,the PCR products were further analyzed by genescan technique to evaluate clonality of the detectable TCR Vβ T cells. The PCR products of the oligoclonal T cells from three cases were analyzed by direct sequencing to define the sequence of CDR3.Results The expression pattern of TCR Vβ repertoire in different individuals are different. Vβ2-21 subfamilies could be detected in CML cases. The frequent usage Vβ repertoire in CML was Vβ1,Vβ2 orVβ13. Most of the PCR products from 27 patients displayed polyclonality,while a part of the PCR products from 21 out of 27 samples displayed clonal expansion pattern. The clonal expanded T cells in CML could be found in Vβ16 subfamilies. The frequent usage of Vβ genes in clonal expansion was Vβ3,Vβ13 or Vβ21. Multiple Vβ clonal expansion was a general phenomenon in the same patient. The CDR3 sequence of Vβ21 oligoclonal T cells from 3 cases showed some difference in splice regions and in the usage of J segments.Conclusions These results indicated that clonal expanded T cells could be found in patients with CML and were tendentious in Vβ3,Vβ13 and Vβ21 subfamilies that may be related to the specific immune response for leukemia cell associated antigen. Background In general, it is very important to understand the state of T cell immune response against tumor cells in leukemia patients and it is particularly critical to assess the T cell repertoire of untreated patients. As we know, few studies have dealt with the distribution of oligoclonal T cells in leukemia, so we investigated the distribution and clonality of TCR Vβ repertoire of T cells in patients with chronic myelogenous leukemia (CML) in chronic phase. Methods The complementarity determining region 3 (CDR3) of TCR Vβ24 subfamily genes were amplified in The order of observe the distribution of TCR Vβ repertoire, the PCR products were further analyzed by genescan technique to evaluate clonality of the detectable TCR Vβ T cells. The PCR products of the oligoclonal T cells from three cases were analyzed by direct sequencing to define the sequence of CDR3.Results Vβ2-21 subfamilies could be detected in CML cases. The frequent usage of Vβ repertoire in CML was Vβ1, Vβ2 or Vβ13. Most of the PCR products from 27 patients showed polyclonality, while a part of the PCR products from 21 out of 27 samples displayed clonal expansion pattern. The clonal expanded T cells in CML could be found in Vβ16 subfamilies. The frequent usage of Vβ genes in clonal expansion was Vβ3, Vβ13 or Vβ21. Multiple Vβ clonal expansion The CDR3 sequence of Vβ21 oligoclonal T cells from 3 cases showed some difference in splice regions and in the usage of J segments. Conclusion These results indicated that clonal expanded T cells could be found in patients with CML and were tendentious in Vβ3, Vβ13 and Vβ21 subfamilies that may be related to the specific immune response for leukemia cell associated antigen.