There are two ways of immune reactions, one of which is humoral immunity and the other cell-mediated immunity. Neoplastic disease in man is often accompanied by defective cellular immunity, as manifested by tests for cutaneous delayed hypersensitivity. Sensitization test with 2,4-dinitrochlorobenzene (DNCB) and used routinely as a measure for cell-mediated immune reactivity. Dinitrochlorobenzene skin testing is a most useful probe into assessment of the cell mediated immunocompetence of cancer patient. In an attempt to evaluate the cell-mediated immunity in cancer patients of E.N.T. field, dinitrochlorobenzene, a compound which uniformly induce hypersensitivity in normal individuals, had been used in the present study in the Dept. of E.N.T., S.N.U.H. from Jan.'75 to Sept.'75. Cellular immune responses in 43 patients with malignant disease of E.N.T. field were compared with those in 65 healthy controls using quantitative DNCB contact sensitization. Differences were demontrated between malignant patients and controls at all levels of reactivity measured. The following results were obtained. 1) Malignant patients had a lower incidence of spontaneous flare reaction (10.6 vs. 87.7% in controls), a higher incidence of impaired reactivity (34.0 vs 6.1% in controls), and a higher incidence of anergy (55.4% vs 6.2% in controls). In malignant patients, 26 of the 47 cases (55.4%) had anergic reaction. In L.M.G. patients, 5 of the 8 cases (62.5%) had anergic These results showed decreased contact sensitivity, compared the controls which 4 of the 65 cases (6.2%) had anergic, which suggested some defect, in the cell-mediated immunity in patients with malignant disease and those with L.M.G. 2) Distribution of age and sex of 47 patients with malignant disease was no significant relationship. 3) While abnormal reactivity occurred in all tumor locations and tumor histologic types studied, a significant relationship was shown between tumor location and quantitative DNCB reactivity. Reactivity was more abnormal in patients with malignancy of floor of mouth, nasopharynx, tongue, tonsil; less in patients with malignancy of larynx, maxillary sinus. No significant relationship was shown between histologic tumor types and DNCB reactivity. 4) Peripheral lymphocyte counts were related to the results of dalayed cutaneous hypersensitivity to DNCB. Lymphocytopenia (counts less than 1,000/mm³) in malignant patients with DNCB anergic reactivity was 38.9% (7/18) in impaired reactivity 16.7% (2/12), in malignant patients with spontaneous flare reaction and control group absent (0/3, and 0/36).