Head and neck cancers(H & N Cancers) show a large variety of immunologic alterations, which are different to any other solid tumors, so it is difficult to relate the immunologic alterations with either antineoplastic treatment or the disease itself. But the advent of monoclonal antibodies made possible the identification of distinct T cell subpopulations and natural killer cells(NK cells) and thereby an increased understanding of immunologic responses. And so we evaluated peripheral blood lymphocytes subpopulations and natural killer cells by use of flow cytometry and tried to evaluate any alterations of immunologic parameters in patients with H & N cancers. The results were as follows ; 1) Normal controls vs pretreated patients. In H & N cancers, CD3+cells were declined, but NK cells were increased. 2) Early cases vs Advanced cases. In advanced H & N cancers, CD3+cells and CD4+cells were declined, but NK cells were increased. 3) Pretreated vs Post RT. In patients who underwent radiotherapy, CD3+cells, CD4+cells, and CD4/CD8 ratio were declined, but CD8+cells and NK cells were increased. The decrease in CD4/CD8 ratios in patients who underwent radiotherapy was due to the increase in CD3-CD8+cells.