We report our long-term experience with 104 patients treated for recurrent superficial bladder tumors followed for a mean of 48 ± 2 months (range 6 to 83 months). Patients received 6 weekly intravesical bacillus Calmette-Guerin instillations, and were followed for response with urinary cytology, cystoscopy and bladder biopsy. Patients were considered treatment failures if either urinary cytology or biopsy results were positive for tumor. Of 69 patients who failed the initial treatment course 60 were given an additional 6-week course of therapy. A 6-week course of bacillus Calmette-Guerin was successful in 19 of 55 patients (35%) treated for prophylaxis, 10 of 32 (31%) treated for carcinoma in situ and 6 of 17 (35%) treated for residual tumor. The response rate for the total patient population treated with 1, 6-week course was 34% (35 of 104). Another 6-week course was successful in 32 of 60 patients (53%). The over-all response rate free of tumor for patients treated with either 6 or 12 weeks of therapy was 64%. The mean interval free of tumor was 48 months. We evaluated tumor type, stage and grade in conjunction with muscle invasion to assess potential indicators of response to a second course of bacillus Calmette-Guerin. Of 13 patients with carcinoma in situ and 45 with papillary disease 5 (38%) and 26 (58%), respectively, responded to a second course of bacillus Calmette-Guerin (not significantly different). In contrast, 5 of 8 carcinoma in situ failures (63%) had muscle invasive disease, compared to only 3 of 19 papillary nonresponders (16%) (p < 0.02). These results suggest that intravesical bacillus Calmette-Guerin for the treatment of superficial bladder tumors is an effective long-term therapy. One 6-week course may be ineffective for some patients and another 6-week course provides long-term survival free of tumor for many course 1 failures. Patients who present with carcinoma in situ after a single 6-week course of intravesical bacillus Calmette-Guerin have a significantly higher risk for muscle invasive disease than those with recurrent papillary tumors.