Objective:To study the effect of tumor infiltrating lymphocytes at cancer nest on local control of rectal cancer after preoperative radiotherapy.Methods:From Jan.1999 to Oct.2007,a total of 107 patients with rectal cancer were reviewed.They were treated by preoperative radiotherapy,30 Gy/10 fractions/12 days.Two weeks later,the patient underwent a surgical operation.Their pathological samples were kept in our hospital before and after radiotherapy.Lymphocyte infiltration(LI)degree,pathologic degradation and fibrosis degree after radiotherapy in paraffin section were evaluated under microscope.Results:After followed-up of 21 months(2-86 months),a total of 107 patients were reviewed.Univariate analysis showed that lymphocyte infiltration(LI),fibrosis and pathologic changes after radiotherapy were significant factors on local control.Logistic regression analysis showed that LI after radiotherapy was a significant effect factor on local control.Conclusion:LI,fibrosis and pathologic degradation after radiotherapy are significant for local control of rectal cancer after preoperative radiotherapy.LI after radiotherapy was a significantly prognostic index for local control of rectal cancer after preoperative radiotherapy.