Various reports suggest that most tumors in humans may develop when their immune mechanism is depressed. The results generally indicated that some immunological change occurs in cancer patients in connection with the presence of malignant tissue, prabaly suppressing the native resistance mechanism of the patient against cancer. Some reports suggest that radiotherapy a common modality for the treatment of the cervical cancer, may have deleterious effects on the host immunity, but there still remains much disagreement between many researchers. In the present study, we have attempted to demostrate the effects of radiotherapy on the immune capacity of cervical cancer patients by immune aswssment. From the patients with carcinoma of the uterine cervix, who visited to the department of Obstetrics and Gynecology, Yonsei university, College of Medicine, from Novemher 1986 through October 1988, 32 patients were selected for this study. The 20 healthy controls were selected from people whose age and characteristics were similar to patients. T and B lymphocyte count., peripheral blood lymphocyte mitogenic response to phytohemagglutinin (YIIA) and concanavalin A (Con Al, natural killer cell activity and antibody dependent cell-mediated cytotoxicity were evaluated in this study. Immune assessment were performed on all patients before treatment, and 1, J, 6, 12 months of follow-up visits after completion of treatment in 20 patients, and the result. were as follows; 1) The measurcd T and B lymphocyte counts in the study subjects were a little low compared with those of controi subjects; the differences, however, was not significant. Lymphocyte mitogenic response to PHA and Con A, antibody dependent cell-mediated cytotoxicity and notural killer cell activity were significantly depressed; however, immune capacity compared according to the disease stage showed no remarkable difference. 2) T and B lymphocyte counts showed a decrease from 1 month foilowing radiotherapy and recovcry did nut occur until the 12 months follow-up. 3) Lymphucyte mitogenic response tu PHA and Cun A were sightly depressed from I month following radiotherapy and no significant difference was noted during follow-up. 4) Lymphocyte mitogenic respr>nse to Con A was slightly depressed after 1 month foliowing radiotherapy, and its recovery, though minimal, was noted from 6 month following radiotheyapy, but still was significantly low as compared with that of control. 5) Antibody dependent cell-mediated cytotaxicity showed no significant difference both before and after radiotherapy, but natural killer cell activity was depressed from 1 month after treatment with further depression being noted at 12 months follow-up. Immune status in the cervical cancer patients in this study, as evidenced by the depression of many of the parameters studied, appears to have been impaired, which was similar to those noted elsewhere in patients with various other cancers. Radiotherapy apparently caused further impairment of immunity in our patients. During the one year follow-up after radiotherapy, the number of T and B lymphocytes, lymphocyte mitogenic response to PHA, and NK cell activity of our patients all remained unreverted ta their pretreatment levels. Whether these values change to those of the controls or at least to their pretreatment levels is uncertain at this point and should require further follow-up.