Objective: To study T cell immunology in patients with colorectal cancer, the molecular features of clonal expanded T cell in TIL and PBL were analyzed by assessment of TCRb gene reopertoire. Methods: The rearranged V-J genes of TCRb chain were amplified by RT-PCR and separated with denaturation polyacrylamide sequencing gel eletrophoresis. The PCR products were sequenced directly to determine the characteristics of the clonal expanded transcripts. Results: There were oligoclonal expanded transcripts of TCRb V genes both in TIL and PBL from pre- operation patients, which all disappeared in PBL after operation. The amino acid sequences of the CDR3 regions in these oligoclonal expanded T cells suggested that they related with the tumor peptide-specific activation. Existence of clonal expanded T cells in PBL may have relevance with the recurrence. Conclusion: Tumor peptide-specific Activated T cell clones were found not only in TIL of colorectal cancer tissue, but also in PBL of tumor-bearing patients. The activation of systemic T cell immunology may play an important role in the prognosis of patients. Objective: To study T cell immunology in patients with colorectal cancer, the molecular features of clonal expanded T cell in TIL and PBL were analyzed by assessment of TCRb gene reopertoire. Methods: The rearranged VJ genes of TCRb chain were amplified by RT-PCR and The PCR products were sequenced directly to determine the characteristics of the clonal expanded transcripts. Results: There were oligoclonal expanded transcripts of TCRb V genes both in TIL and PBL from pre- operation patients, which all disappeared in The amino acid sequences of the CDR3 regions in these oligoclonal immunization T cells suggested that they related with the tumor peptide-specific activation. Existence of clonal expanded T cells in PBL may have relevance with the recurrence. Conclusion: Tumor peptide- specific Activated T cell clones were found not only in TIL of colorectal cancer tissue, but also in PBL of tumor-bea ring patients. The activation of systemic T cell immunology may play an important role in the prognosis of patients.