To treat superficial bladder cancer or invasive bladder cancer presenting as a solitary tumor, conservative therapy such as transurethral resection of bladder tumor or partial cystectomy has long been carried out. We studied the effect of 1-hexylcarbamoyl-5-fluorouracil (HCFU), and the effects of the combination of HCFU and 2.5-di-O-acetyl-D-glucaro-(1-4)(6-3) dilactone (SLA) which is an anti-beta-glucuronidase agent, for preventive therapy. In the patients treated with HCFU, the recurrence rate was 3.6% and 26.6% one year and two years, respectively, after conservative operation. In the patients treated with both SLA and HCFU, the recurrence rate was lower than in those treated with HCFU one year or more after conservative operation, and a long-term preventive effect was expected for nondrinkers.