OBJECTIVE: Free hand insertion of an external ventricular drain (EVD) is one of the most common emergency neurosurgical procedures, usually performed on critically ill patients. Complications such as infection and hemorrhage that accompany the placement of an EVD have been studied thoroughly, but few reports have focused on the accuracy of EVD positioning. As a result, the authors of this paper retrospectively studied the accuracy of tip positioning in the placement of an EVD. METHODS: One hundred and thirteen emergency EVDs were performed through Kocher's point during the past 3 years. All patients underwent the following procedures: at least one routine post-EVD computed tomographic (CT) scan that was retrospectively reviewed for accuracy of the EVD tip position, calculation of the Evan's index, and measurement of the intracranial length of the EVD. We divided the EVD tip position into 6 groups as follows:1) ipsilateral frontal horn of the lateral ventricle, 2) contralateral frontal horn of the lateral ventricle, 3) third ventricle, 4) body of the ipsilateral or contralateral lateral ventricle, 5) basal cisterns, or 6) brain parenchyma. Among the 6 groups, only the ipsilateral frontal horn group was considered to be the correct position for the EVD tip. RESULTS: The mean age of the patients was 55.6+/-15.3 years (age range, 12~90 years), and the most common indication for the EVD was supratentorial intracerebral hemorrhage (ICH) and intraventricular hemorrhage (IVH) (57.5%). Forty-five out of a total of 113 EVDs were placed by inexperienced neurosurgical trainees, and the remaining 68 were placed by experienced practitioners. Among 113 post-EVD CT scans, 48 EVD tips (42.5%) were in the ipsilateral frontal horn of the lateral ventricle (considered to be the correct position); 22 (19.5%) were in the third ventricle, 16 (14.1%) in the body of the ipsilateral or contralateral lateral ventricle, 14 (12.4%) in the contralateral frontal horn of the lateral ventricle, 11 (9.7%) within the brain parenchyma and 2 (1.8%) in the basal cistern. The mean estimated EVD length was 57+/-8.4mm. The mean length of EVDs that were positioned in the ipsilateral frontal horn was 55+/-4.3 mm, whereas the mean lengths of EVDs in the parenchyma and basal cistern were 64+/-14mm and 72+/-3.5mm, respectively. In addition, there was no statistically significant relationship between the surgeon's experience and the accuracy of the position of the EVD tip (p > 0.05). CONCLUSION: Emergency free hand placement of an EVD might be an inaccurate procedure. Further multi-institutional prospective studies are required to assess the accuracy and complications of free hand insertion of EVDs in an emergency setting. Studies are also needed on the feasibility of routine use of intra-operative neuro-navigation of other guidance tools, such as ultrasonography.