Purpose: We studied whether a single instillation of epirubicin after transurethral bladder tumor resection would influence the interval to and size of the first recurrence. Materials and Methods: A total of 404 patients from 13 hospitals were randomized to 1 instillation of 50 mg epirubicin or placebo within 6 hours after transurethral resection of bladder tumors. Results: Of 155 evaluable patients in the epirubicin group 79 (51.0%) had recurrence compared to 95 of 152 (62.5%) in the placebo group (p = 0.04). Of the recurrences 63.3% were small (1 to 5 mm). Tumor size was unknown in 5 patients. Of 79 patients with recurrence in the epirubicin arm 33 (42.9%) vs 29 (31.5%) of 95 in the placebo arm had larger (more than 5 mm) first recurrences (p = 0.12). Approximately half of the patients with first recurrences were treated as outpatients and the other half spent a total of 145 days in the hospital with no difference between the groups. Conclusions: We confirmed the results of previous studies showing that 8.5 patients must be treated with a single instillation to prevent I recurrence. Furthermore, our data may indicate that only small recurrences are prevented, which could easily be fulgurated using local anesthesia at followup cystoscopy. The benefit of single instillations can be questioned if this finding is confirmed by others.