Complement-dependent cytotoxic antibodies to three cervical carcinoma cell lines (Me-180, SW-732 and HeLa) and to Herpes simplex virus type 2 (HSV-2)-infected cells were determined in a long-term study of women with cervical carcinoma. Cytolysis of surface antigens differed significantly between the cervical carcinoma cell lines and HSV-2. Regression of the tumor during treatment was accompanied by decreasing cytolysis in the cervical carcinoma lines, while tumor bearers and patients who became severely ill had high or increasing cytotoxic antibodies, The opposite was noted for the antibody response to HSV-2 infected cells: patients with less advanced cancer had significantly higher cytolytic activity than those who were severely ill or had advanced cancer; long-term survivors demonstrated high, stable lysis of HSV-2 infected cells. As a control of the cervical carcinoma cell lines, cytolytic activity was tested also on a lung carcinoma cell line, A-549. No significant differences were found between the patients with cervical cancer and the control women. Tumor bearers and patients treated for advanced cervical cancer showed a slight but non-significant increase in cytolytic activity on the A-549 line.