Non-immunoglobulin G-neutralizing antibodies to herpes simplex virus (HSV) type 2 were assayed in sera adsorbed with Staphylococcus aureus Cowan I. They were present in 8% of women with normal cervical smear and in 20, 41, and 74% of women with atypia, dysplasia, and cervical carcinoma, respectively. Lymphocytes of the patients were tested for in vitro transformation by killed HSV type 1 and HSV type 2 (HSV-2), as well as by mitomycin C-treated hamster cells transformed by HSV or other viruses or not transformed. Specific stimulation by the HSV-transformed cells occurred in 2, 22, and 40% of women with normal cervical smear, dysplasia, and carcinoma of the cervix, respectively. This frequency rose to 82% during treatment with irradiation and decreased to 0% after surgery. When HSV-2 virions were used as antigens to stimulate the lymphocytes, similar differences were found between the various groups, but they were less clear-cut, since 16% of the control women had lymphocytes responding to HSV. Non-immunoglobulin G antibodies to HSV-2 were not present in blood at the same time as cell response to HSV-2-transformed cells. There was also a negative correlation between neutralizing activities of the sera and the indices of lymphocyte stimulation, indicating a regulation between humoral and cell-mediated responses.