Bladder cancer cell lines express both T and sialyl-T antigens. The bladder cancer cell lines, 5637, HT1376, MCR and T24, treated with heat-inactivated neuraminidase (A) or with active neuraminidase (B) were analyzed by Flow cytometry using fluorescent PNA lectin. The gray line shows the controls without PNA. The T antigen is expressed at high levels by the HT1376 and MCR cell lines, but only weakly by 5637 cells and at an intermediate level by T24. According to the results obtained after removing the cell surface sialic acid by neuraminidase treatment, the 5637 and T24 cell lines express the T antigen masked by sialic acid.