Thomsen Friedenreich antigen (T-ag), ABH isoantigen (ABH-ag) in 106 cases with bladder tumor (all transitional cell carcinoma) of various histological grades and stages were investigated by the Avidin-Biotin-Peroxidase Complex (ABC) method. There was a correlation between histological grade, stage and deletion of the antigenicity (T-ag and ABH-ag). In a follow-up study of 45 patients with low grade and low stage tumor, the recurrence rate after surgery of the cases with abnormal antigenicity (T-ag and ABH-ag) was significantly higher than that of the cases with the normal antigenicity. Combination of two markers (T-ag and ABH-ag) was significantly more effective than the single marker.