Thirty-seven cases of superficial bladder cancer were treated with 4'-epi-adriamycin (EPI) by intravesical instillation to investigate the optimal dosage and treatment schedule. Patients were randomized into either group A: 50 mg/day for 6 days (regimen A) or group B: 60 mg/day for 3 days X 2 courses with 4 days interval (regimen B). Seventeen cases were evaluated in both groups, three cases were ineligible in group B. Patient characteristics such as age, sex, size of tumor, stage and grade were not significantly different between the two groups. Response rates were 41.2% (group A) and 70.6% (group B), while incidence of toxicity was 47.1% and 50.0% respectively. There is a trend in favor of regimen B which deserves to be more extensively verified.