BACKGROUND: Intracranial pressure is routinely monitored in patients with severe traumatic brain injury (TBI). Patients with TBI sometimes develop hydrocephalus, requiring permanent cerebrospinal fluid (CSF) diversion. OBJECTIVE: To quantify the need for permanent CSF diversion in patients with TBI. METHODS: Patients who received a ventriculostomy after TBI between June 2007 and July 2008 were identified, and their medical records were abstracted to a database. RESULTS: Sixteen of 71 patients (22.5%) receiving a ventriculostomy required a ventriculoperitoneal or ventriculoatrial shunt before discharge from the hospital. The average number of days between ventriculostomy and shunt was 18.3. Characteristics that predispose these patients to require permanent CSF diversion include the need for craniotomy within 48 hours of admission (odds ratio, 5.20; 95% confidence interval, 1.48-18.35) and history of culture-positive CSF (odds ratio, 5.52; 95% confidence interval, 1.19-25.52). Length of stay was increased in patients receiving permanent CSF diversion (average length of stay, 61 vs 31 days; P = .04). Patient discharge disposition was similar between shunted and nonshunted patients. CONCLUSION: In this retrospective study, 22% of TBI patients who required a ventriculostomy eventually needed permanent CSF diversion. Patients with TBI should be assessed for the need for permanent CSF diversion before discharge from the hospital. Care must be taken to prevent ventriculitis. Future studies are needed to evaluate more thoroughly the risk factors for the need for permanent CSF diversion in this patient population.