Carcinoma in situ is a form of superficial transitional cell carcinoma, which is characterized by a lateral spread along the bladder epithelium, with high-grade malignancy and poor prognosis. Early radical cystectomy is considered the definitive treatment even in the absence of associated invasive cancer. In six prospective phase II studies, 123 carcinoma in situ patients were administered intravesical TICE bacillus Calmette-Guerin (BCG). Treatment consisted of at least six weekly instillations (induction) followed by twelve monthly instillations (maintenance) of BCG (50 mg: 1 to 8 x 10(8) colony-forming units). Of 119 evaluable patients, 90 (76%) achieved complete remission including 45 of 63 (71%) patients who received prior intravesical chemotherapy. Forty-five responders (50%) remain in complete remission with negative urine cytology with a median duration of response projected to be greater than or equal to forty-eight months. There is no difference in survival between BCG responders and nonresponders, but there is a significant difference in cystectomy rates: 10 of 90 (11%) responders vs. 16 of 29 (55%) nonresponders (P less than 0.0001, Fisher's exact test) and time to cystectomy (31 vs. 74 mos.) (P less than 0.001, log-rank test). Delaying cystectomy does not seem to affect survival and improves quality of life. Treatment was well tolerated with some major adverse effects. Intravesical TICE BCG is an effective treatment for bladder carcinoma in situ patients with or without prior chemotherapy.