A prospective, randomized trial was conducted to evaluate and compare the effects of modified adjuvant intravesical bacillus Calmette-Guérin (BCG) and epirubicin regimens in patients with superficial bladder cancer. One hundred thirty-two individuals with recurrent and/or multiple neoplasms, i.e. at high risk for tumour recurrence and progression, were enrolled. After complete transurethral resection of their tumours, the patients received a 6-week course of BCG instillations or an early 4-week course of epirubicin instillations as their initial therapy. Those with stage Ta and grade 1 neoplasms who remained free of recurrences received maintenance therapy consisting of single quarterly instillations. However, for those with stage T1 cancer of any grade or stage Ta of grade 2 or 3 neoplasms who also remained free of recurrences, the treatment schedules were modified: they received, instead of single maintenance doses, 3 weekly instillations of epirubicin at months 3 and 6 of follow-up, or a 3-week course of BCG at month 6 of follow-up. The recurrence-free rates did not differ significantly between the two study groups (44% for epirubicin versus 55% for BCG), for an identical median follow-up of 43 months. However, in terms of relative risk of recurrences, disease-free intervals and recurrence rate per 100 patient-months, a significant benefit in favour of BCG when compared with epirubicin was demonstrated in patients who had stage T1 or grade 3 neoplasms.