Immunological phenotypes of lymphocytes from peripheral blood of 100 patients with different stages and histologies of cancer of the uterine cervix were analyzed using monoclonal antibodies and F(ab)2 fragments of antihuman immunoglobulin. The T lymphocyte population was decreased in advanced cases of the cancer along with a rise in the B cell numbers. The OKT4+ cells generally showed a decrease in the cancer patients in contrast to the increase shown by the OKT8+ cells. The OKT4/OKT8 ratio was altered in this cancer except in patients with stages I and IIA. In terms of histology, the poorly differentiated tumors showed a higher imbalance of the cellular composition when compared to the well-differentiated and moderately differentiated tumor-bearing patients. These findings point toward a possible alteration in the immune effector cells of these cancer-bearing patients.