The response of patients with superficial transitional cell carcinoma of the bladder (STCB) to intravesical chemotherapy is variable; some patients enjoy a long period without recurrence, whereas others have recurrence of tumor within 2 years of removal of the primary lesion. Previously, others have demonstrated that the loss of normal cell surface antigens, such as ABO(H) blood group antigens or beta-2 microglobulin (B2M) has been correlated with more aggressive behavior by tumor. In this study, using immunohistochemical techniques, the authors evaluated the initial pretreatment biopsy specimen of bladder tumors for the presence of ABO(H) antigens and B2M. Data from this sample patient population, all with biopsy-proven STCB, indicate that expression of these two markers is predictive of a therapeutic response to prophylactic intravesical bacillus Calmette-Guerin (BCG) (Tice strain) after resection, and that expression of the two markers is of greater predictive value than expression of either antigen alone.