Abstract: The changes in lymphocyte subsets from 50 patients with colon cancer (25 patients with grade I and 25 patients with grade II) and 50 normal individuals were determined using flow cytometry. Flow cytometric immunophenotyping by direct and indirect immunoflourescence method was conducted using monoclonal antibodies to CD3 (T-lymphocytes), CD4 (helper/inducer T-cells) and CD8 (suppressor/cytotoxic T-cells) cell surface markers. Immunophenotyping of patients with colon cancer showed a significant decrease (p<0.001) in blood T-lymphocytes CD3 and helper/inducer T-cells CD4. Percentage of CD8 T-cells in colon cancer patients increased but did not reach to a statistical significant. A difference in lymphocyte subsets (CD3 and CD4) in GI and GII with high significance p<0.001 was shown compared with the control. CD4/CD8 ratio for healthy controls was (1.44±0.88) and decreased in colon cancer (1.36±0.93) without significance differences, however the difference between GII colon cancer and the control was highly significance p<0.001. In conclusion, colon cancer may associate with Dysregulation of cellular immune response and that T-lymphocytes subsets may play a role in the immunopathogenesis of colon cancer.