Intravesical chemotherapy will cause complete regression of existing papillary tumor in one third to one half of patients. Controlled clinical trials have demonstrated that chemotherapy reduces the short-term incidence of tumor recurrence by 15% to 18%, but by 5 years, the number of patients suffering tumor recurrence is equal to that in patients treated with surgery alone. Tumor progression cannot occur in the absence of tumor recurrence, but existing studies of intravesical chemotherapy have failed to demonstrate significant reduction in disease progression or mortality rate with treatment. Immunotherapy has the advantage of a mechanism of action different from that of cytotoxic chemotherapy. Immunotherapy with BCG has resulted in complete tumor regression in one half or more of treated patients with papillary tumors and in more than 70% of those with CIS. Controlled studies similarly demonstrate a significant reduction in tumor recurrence, and protection from tumor recurrence has been observed to persist for 5 years or more. At the present time, data remain limited, but three controlled studies have found statistically significant reductions in the rate of disease progression, and one has found a significant reduction in the mortality rate, with BCG immunotherapy. These observations provide convincing evidence that immunotherapy is the treatment of choice for patients with aggressive superficial tumors and suggest that the development of immunotherapeutic alternatives to BCG is likely to be rewarding.