Flow cytometric analysis was made of a tumor-antigen, TA-4, in cells from squamous cell carsinoma of the utrine cervix. The cells were stained by the indirect immunofluorescent antibody technique using a rabbit antibody specific to TA-4 and fluorescein isothiocyanate conjugated anti-rabbit IgG antibody. FCM histograms of the carcinoma cells showed a broad but conspicuous pesk with intense fluorescence pattern not seen in normal squamous epithelium. Would be possible to distinguish malignant from non-malignant cells of the uterine cervix it by the FCM analysis. Possible application of the technique to cytological screening of cervical cancer is discussed.