A streptococcal preparation, OK432 was evaluated as the adjuvant immunotherapeutic agent for superficial bladder tumors. Twenty-nine cases were treated with complete transurethral resection and then randomized prospectively into two groups. One group had adjuvant therapy of OK432 intradermal administration and another group had no adjuvant therapy. OK432 administration significantly reduced the recurrence rates as compared to the control group. Although further studies were required for its full significance, in a short-term study, OK432 intradermal administration produced a beneficial effect in reducing the recurrence rates.