Intravesical instillation of Tokyo 172 strain bacillus Calmette-Guerin (BCG) after transurethral resection of bladder tumor (TUR-Bt) was applied to 35 patients with superficial bladder cancer. The patients received 80 mg of BCG in 40 ml saline infused into the bladder once a week for 6 weeks. Actuarial non-recurrence rates for all 35 patients were 81.7% and 58.4% at one and two years after the BCG therapy, respectively. The recurrence of the bladder cancer after the BCG therapy was observed in 12 patients 3-27 months later. Seven patients received an additional course of BCG instillation, and 6 (86%) showed no further recurrence. Thus, the overall success rate of 2 cycles of BCG instillation was 83% (29 of 35 patients). Moreover, in some cases intravesical BCG instillation was effective for recurrent superficial bladder cancer after intravesical instillation of anti-cancer agents and prolonged the period until recurrence. The progression rate was only 5% (2 of 35 patients). These results suggest that intravesical BCG therapy for superficial bladder cancer helps prevent disease progression.