BACKGROUND: This study seeks to evaluate the relationship between the risk of symptomatic hemorrhage from ventriculostomy placement and International Normalized Ratio (INR) in patients who received a ventriculostomy after traumatic brain injury. METHODS: Patients who received a ventriculostomy after traumatic brain injury between June 2007 and July 2008 were identified and their medical records were abstracted for information. RESULTS: At the time of ventriculostomy placement, 32 patients had an INR<1.2, 26 patients had an INR 1.2 to 1.4, 12 patients had an INR 1.4 to 1.6, and one patient had an INR>1.6 (INR=1.61). No significant difference in the risk of hemorrhage between the groups was observed: 9.4%, 3.9%, 8.3%, and 0%, respectively (p=0.73). In a subgroup analysis of patients who received ventriculostomy in the Neurosurgical Intensive Care Unit within 24 hours of admission (n=54), the average time between admission and ventriculostomy placement in patients who did not receive fresh frozen plasma was 6.8 hours compared with 9.3 hours (p=0.03) for those who did. CONCLUSIONS: In this retrospective study, INRs between 1.2 and 1.6 appeared to be acceptable for a neurosurgeon to place an emergent ventriculostomy in a patient with traumatic brain injury.