Anaemia is considered a common problem in many cancers secondary to the disease itself or related to chemo- and/or radiotherapy. Several clinical trials have advocated the prognostic value of anaemia and hypoxia in the outcome of many cancers. Erythropoietin is recognised as an effective treatment for anaemia, which also improves the quality of life in patients with malignant disease. External radiotherapy plays an important role in the treatment of loco-regional cancer but its efficacy can be compromised by many factors. Tumor hypoxia is considered by many authors as an important factor contributing to radioresistance. We report in this article the radiobiological rationale in favour of combining radiotherapy and erythropoietin, and review relevant clinical papers published in this field.