This study was conducted to compare the effect of intravenous (Venofer) and oral iron on hemoglobin (Hb) rise in response to synthetic erythropoietin in hemodialysis patients. In this controlled single blind clinical trial, 42 hemodialysis patients with < 10 g/dl hemoglobin after seven weeks treatment with 2000 units subcutaneous erythropoietin (three times weekly at the end of each dialysis session) were selected via convenience sampling method. Also at least six mounts history of hemodialysis was necessary for including to the study. Bone marrow malignancy, evidence of chronic infection, evidence of significant bleeding (decrease in Hb level > 2g/dL during the past 3 months), hemoglobinopathies, myelodysplastic syndrome were lead to exclusion of subjects from the study. One week after the last dose of erythropoietin injection, basic measurement was done for serum levels of hemoglobin, ferrtin and iron saturation. Then patients randomly allocated into two oral and intravenous iron groups. For oral iron group patients administrated Ferrous Sulfate tablet 50 mg daily, for seven weeks and other group received 100 mg Venofer, three times weekly at the end of each dialysis sessions for seven weeks and during this time, subjects in both groups received 2000 unit subcutaneous erythropoietin (three times weekly at the end of each dialysis sessions). Finally, hemoglobin, ferrtin and iron saturation were examined following therapy.