The administration of recombinant human erythropoietin (EPO) has considerably improved renal anemia in hemodialysis patients. However, there is a possibility that plasma flow will decrease and cause a reduction of hemodialysis efficiency after the improvement of anemia. In the present study, we examined the influence of the improvement of anemia by EPO administration on the efficiency of dialysis in 44 hemodialysis patients with renal anemia (21 males and 23 females; mean age: 59.5±14.6 years). Epo was administered at a dose of 3, 000 units three times a week and the duration of treatment was generally 12 weeks. EPO treatment significantly improved anemia. However, the blood urea nitrogen, creatinine, and uric acid levels before and after dialysis as well as the potassium and phosphorus levels before dialysis showed no significant changes after the improvement of renal anemia. Accordingly, it is unnecessary to take any specific measures to improve the efficiency of dialysis after treating renal anemia with EPO.