An indirect immunofluorescence assay is described which specifically detects antibodies against cervical carcinoma-associated membrane antigens. Cells from the ME-180 cervical carcinoma cell line were used as target cells. Sera had to be absorbed with pooled tonsillar lymphocytes prior to use, to remove nonspecific antibodies. The antibody was detected in 61 of 74 patients (82%) with invasive squamous cell carcinoma of the uterine cervix and in 5 of 65 controls (8%). A group of 49 patients with early or preneoplastic stages of this tumor (microinvasive carcinoma, carcinome-in-situ, and dysplasia) did not differ from the control group in the incidence of the antibody (5 of 49 patients, 10%). It is concluded that the occurrence of this antibody is specific for cervical carcinoma (P < 0.001). However, the assay cannot be used as a diagnostic marker for preneoplastic stages of this tumor.