PURPOSE: The incidence, etiology, and management of cancer-related anemia is reviewed and the role of i.v. iron therapy in its treatment is described. SUMMARY: Between 30% and 90% of patients with cancer develop anemia due to direct effects of the disease, its treatment, underlying nutritional deficiencies, and the inflammation that characterizes chronic disease. Although the use of erythropoiesis-stimulating agents (ESAs) increases hemoglobin levels and decreases the need for transfusions, up to 50% of patients do not to respond to these drugs, usually due to the presence of absolute or functional iron deficiency. Multiple clinical trials have demonstrated that i.v. iron supplementation in patients with cancer-related anemia improves the response rate to ESAs, reduces the time to target hemoglobin levels, decreases ESA requirements, reduces costs, and is more efficacious than oral iron. These benefits are seen without increased toxicity. Nonetheless, i.v. iron remains underused in patients with cancer, partly due to misinformation and misinterpretation of the clinical nature of adverse events. CONCLUSION: Intravenous iron is underutilized in patients with cancer-related anemia. Based on published evidence, i.v. iron supplementation in patients with absolute or functional iron deficiency can improve patient responses to ESAs and reduce ESA requirements and may also reduce the need for transfusions and improve quality of life.