Background: Anemia is the most common problems in chronic kidney disease especially dialysis patients. Anemia is also the important risk factors of cardiovascular morbidities and mortality in these patients. Iron deficiency is the most common cause of erythropoietin hypo responsiveness. Intravenous iron supplement had a benefit on improvement of anemia parameters and decreased erythropoietin dose in chronic hemodialysis patients. However, indication and schedule of intravenous iron supplement are different in several clinical practice guidelines. This study was conducted to explore the benefit of Intravenous iron supplement on anemia and erythropoietin dose in chronic hemodialysis patients in Thailand. Methods: The multicenter randomized controlled trial was conducted in 194 chronic hemodialysis patients in 5 dialysis centers. The participants who had serum ferritin 200-400 ng/ml and serum transferrin saturation< 30% were randomized to low ferritin ( serum ferritin 200-400 ng/ml) and high ferritin (serum ferritin 500-700 ng/ml). During run-in period (-8 weeks), intravenous iron 100 mg was given every week for 6 weeks in high ferritin group, and no iron prescription in low ferritin group. During 6 months observation period, intravenous iron prescription was given to keep serum ferritin as study protocol. Anemia parameters, iron dose and dose of erythropoietin were monitored. 61 Results. 96 participants were randomized to keep target serum ferritin 200-400 ng/ml and 98 participants were randomized to keep target serum ferritin 500-700 ng/ml. Baseline characteristics between two groups were not different. During run-in period, the mean hemoglobin was 9.1±1.4 g/dl, mean erythropoietin was 7105.1±2279.1 unit/week in low ferritin group and the mean hemoglobin was 10.0±1.7 g/dl, mean erythropoietin was 6262.5±2467.0 unit/week in high ferritin group ( P<0.05). At baseline, the mean hemoglobin was 8.9±1.3 g/dl, mean erythropoietin was 7331.2±2118.1 unit/week in low ferritin group and the mean hemoglobin was 9.8±1.8g/Dl, mean erythropoietin was 6347.1±2663.1 unit/week in high ferritin group (P<0.05). During 3 month follow up, the mean hemoglobin was 9.0±1.3 g/dl, mean iron dose was 318.8±78.8 mg/3 months, mean erythropoietin was 6946.6±1837.1 unit/week in low ferritin group and the mean hemoglobin was 9.8±1.6 g/dl (P<0.05). mean iron dose was 595.3±216.1mg/3 months (P<0.05), mean erythropoietin was 6587.4±2956.1 unit/week (P=0.55) in high ferritin group. However, the mean different change between two groups did not reach statistical significance at 3 months follow up (Hb 2.8±13.0% vs Hb 1.6±15.1%, P=0.625, erythropoietin dose -1.9±16% vs 8.1±30.4%, p=0.099 ). At the end of treatment, the mean hemoglobin was 9.4±1.4 g/dl in low ferritin and 10.1±1.4 g/dl in high ferritin (P=0.04). Conclusion: Intravenous iron prescription keeping serum ferritin 200-400 ng/ml or 500-700 ng/ml seem to maintain hemoglobin and require erythropoietin dose as the same benefit. However, the mean iron dose 100 mg/month and 200 mg/month should be prescribed to keep target serum ferritin 200-400 ng/ml and 500-700 ng/ml in Thai chronic hemodialysis patients. Therefore, at least 100 mg intravenous iron supplement every month should be used to maintain serum ferritin around 500 ng/ml.