Objective : Post-traumatic hydrocephalus is a complication of head injury and can present with several different clinical symptoms. However, the developing factors of post-traumatic hydrocephalus and treatment are still not well known. The authors design the study to focus on incidence, causing diseases and treatment of post-traumatic hydrocephalus. Methods : The 789patients of traumatic head injury followed by admission treatment over 7days from Jan. 1997 to Dec. 2001, were divided shunt group and shunt free group. We analyzed age, sex, causing diseases, developing time of hydrocephalus and effects of shunt operation in post-traumatic hydrocephalus. Results : The incidence of post-traumatic hydrocephalus for requiring shunt was 9.2% [64cases]. Chronic hydrocephalus which developed after 14days of injury was higher incidence [51cases]. We found following variables were significantly related to shunt-dependent hydrocephalus : low GCS score at admission, initial CT finding of traumatic subarachnoid hemorrhage and intracerebral hemorrhage [including intraventricular hemorrhage]. The effect of shunt operation was not related with the spinal pressure, but had statistically significant correlation with the response of lumbar drainage. Conclusion : We conclude that development of hydrocephalus after head trauma is related to low GCS score, intracerebral hemorrhage [including intraventricular hemorrhage] and subarachnoid hemorrhage. The effect of preoperative lumbar drainage has a significant role in predicting the result of shunt operation in patient with post-traumatic hydrocephalus.