Anticomplement immunofluorescence (ACIF) technique was applied to Herpes simplex virus type 2 (HSV-2)-transformed cells (333-8-9) and to cells lytically infected with HSV-2 in sera from women with cervical carcinoma. There was a correlation between the positive results with both types of cells. Long-term survivors suffering from cervical cancer showed a high percentage of positive immunofluorescence (IF) reactions in HSV-2 transformed cells (77%) as well as in cells lytically infected with HSV-2 (77%) in sera obtained before treatment. The figures were 81 and 83% respectively in sera collected 6-24 months after treatment. When the IFs of survivors and non-survivors were compared, the survivors showed more cytoplasmic staining reactions in sera obtained before treatment than in similar sera from non-survivors, whereas there was no difference in nuclear IF. The sera of survivors taken 6-24 months after treatment had a significantly higher overall fluorescence rate than similar sera from non-survivors. In late sera taken 36 months after treatment, a drop in reactivity was noted for the survivors to values comparable with those obtained from non-survivors. The controls (age-matched, healthy women and patients with malignancies other than cervical carcinoma) showed significantly less IF reactions (P less than 0.001).