Intravesical instillation of epirubicin was carried out to investigate the efficacy of this treatment in preventing postoperative recurrence of superficial bladder cancer. The subjects were 100 patients who had been treated with transurethral resection (TUR) for superficial transitional-cell carcinoma of the bladder (classified as primary or recurrent superficial bladder cancer of pathological stage Tis, Ta, or T1 and histological grade G1, G2, or G3) at Tokyo Women's Medical College Hospital and its affiliated hospitals during the 2-year period ranging from April of 1990 through March of 1992. A solution of epirubicin was prepared by dissolving 20 mg in 30 ml physiological saline, and this was instilled into the bladder a total of 17 times during 1 year: once immediately after TUR, once every 2 weeks for the next 4 months, and then once per month for the following 8 months. Thereafter, the course of each patient was followed by performing urinary cytodiagnosis once each month and cystoscopy once every 3 months. Of the 100 patients, 83 were evaluable. The mean duration of follow-up was 461 +/- 222 days, and the recurrence rate was 30.1% (25/83 cases). The recurrence rate determined for primary cases was 19.7%, whereas that recorded for recurrent cases was 61.9%. Adverse effects occurred in 9.3% (9/97) of the patients, but these side effects were mild in severity and the instillation regimen did not have to be discontinued in any of the patients. Analysis of the risk factors for recurrence revealed significantly higher recurrence in the recurrent-patient group and the multiple-tumor group. On the basis of these findings, the authors surmised that when given in an intravesical instillation regimen, epirubicin causes few adverse effects, and its efficacy in the prophylaxis of recurrence of superficial bladder cancer is equivalent to that thus for reported for other drugs. At present, the authors are carrying out a controlled clinical study on epirubicin that takes into account the risk factors for recurrence of superficial bladder cancer.