We evaluated the effects of 4'-epi-Adriamycin (EPI), a derivative of Adriamycin (ADR), in intravesical instillation chemotherapy. The patients received two courses of three daily instillations of 50-80 mg EPI dissolved in 30 ml physiological saline on 3 consecutive days, with an interval of 4 days between courses. Full evaluation was possible in 33 of 35 patients with superficial bladder tumors treated with EPI. Complete response was observed in 4 cases and partial response in 14 cases, giving a response rate of 55%. Side effects such as pollakiuria and pain on micturition occurred in 9 cases. EPI appears to be an effective agent for intravesical instillation chemotherapy in patients with superficial bladder tumors.