Anemia in cancer patients is frequent but often underestimated. Anemia affects the health-related quality of life and impacts prognosis and outcome of therapy. Treatment options include the administration of hematopoietic growth factors and red blood cell transfusions. Blood transfusions result in rapid but often transient improvement of anemia. Administration of epoetin or darbepoetin alfa increases hemoglobin levels, decreases blood transfusions, and improves quality of life in patients with cancer. Presently, trials investigate whether treatment of anemic cancer patients with erythropoietin impacts on outcome of chemo- and/or radiotherapy and on overall survival. Oncologists must be aware of the clinical relevance of anemia and offer adequate treatment options to their patients. Supportive treatment of anemic cancer patients presenting anemia-related symptoms should be performed to reduce symptoms in cancer patients and optimize outcome to anticancer therapy.