The purpose of this study is to investigate the effect of erythropoietin on size of brain lesions and outcome in patients with severe head injury. Severe brain-injured patients (Glasgow coma scale less than or equal to 8) with a single brain lesion volume less than 30 ml or those who have diffuse axonal injury are to be included and those who need surgical operation, polycythemic cases and those may not be followed during the project will be excluded from the study. Brain-injured cases with occurrence time more than 8 hours also are not to be included. In this double-blind study 60 patients will be randomly divided into two groups of 30. Patients in intervention group will be received erythropoietin 33000 IU in 50 ml normal saline during 30 min as an infusion. Erythropoietin will be repeated in the same dose 24 and 48 hours later. In another arm of the study, normal saline will be infused instead of erythropoietin as placebo. All of the patients will be checked for CT- Scan and laboratory tests including, hematocrite, hemoglobin, complete blood count, platelet count, ferritin and iron levels, electrolytes, glucose, blood urea nitrogen and creatinine before, 15 and 30 days after intervention and results will be recorded. Patients will be called 3 and 6 months after the beginning of the study, and their Glasgow outcome score will be recorded. Finally, analysis will be performed and patients' results will be compared regarding brain lesion size and outcome.