We treated 40 patients with superficial bladder cancer via intravesical bacillus 
Calmette-Guerin for 1) prophylaxis against tumor recurrence, 2) residual 
carcinoma or 3) flat carcinoma in situ. A single course of intravesical bacillus 
Calmette-Guerin therapy was successful in 6 of 11 patients (55 per cent) treated 
for residual carcinoma and 6 of 12 (50 per cent) treated for carcinoma in situ. 
Of 17 patients receiving a single course of bacillus Calmette-Guerin for 
prophylaxis 11 remained free of tumor during short-term followup. A second 
course of therapy was administered to failures in each treatment category, which 
resulted in favorable responses in 5 of 6 patients treated for prophylaxis, 2 of 
5 treated for residual tumor and 3 of 6 treated for carcinoma in situ. Over-all 
complete responses were achieved in 16 of 17 patients (94 per cent) treated for 
prophylaxis, 8 of 11 (73 per cent) for residual carcinoma and 8 of 12 (66 per 
cent) for carcinoma in situ, with a mean followup from the final treatment of 
9.3, 12.3 and 7.9 months, respectively. Favorable results occurred more 
frequently among patients who exhibited a granulomatous inflammatory response in 
the bladder and delayed hypersensitivity skin test response to purified protein 
derivative. Marked variability in viability of bacillus Calmette-Guerin 
organisms was observed among different lots of bacillus Calmette-Guerin, and a 
direct relationship was observed between bacillus Calmette-Guerin vaccine 
viability and therapeutic efficacy. Most patients who failed initial therapy 
with a low viability lot of bacillus Calmette-Guerin responded favorably to 
re-treatment with a higher viability lot. The results suggest that the level of 
viability of each lot of bacillus Calmette-Guerin vaccine should be verified 
before clinical use.