OBJECTIVE: Preoperative extra-ventricular drainage in poor grade aneurysmal subarachnoid hemorrhage (SAH) patients has been known to improve patient's clinical grade. However, the risk of rebleeding due to increase of transmural pressure hinders its popular clinical use. The authors present new experience of preoperative extra-ventricular drainage in poor grade aneurysmal SAH. MATERIALS AND METHODS: From January 1996 to November 2001, 56 SAH patients underwent extra-ventricular drainage preoperatively. The mean age was 57.9 years (range 27 to 88). Hunt and Hess grade (HH grade) on the time of extra-ventricular drainage insertion were grade 3 in 4 patients, grade 4 in 35 patients and grade 5 in 17 patients. The overall clinical outcome of the patients who underwent extra-ventricular drainage and final clinical outcome according to the intervals between ventricular drainage and direct clipping/endovascular coiling were analysed retrospectively. RESULT: Twenty-six patients (46.4%) improved clinically (average HH grade was improved from 4.6 to 3.3), 25 patients (44.6%) have not been changed, 5 patients (9%) aggravated (4 to 5) after ventricular drainage. Seven of 30 unchanged or aggravated patients underwent CT scan which revealed rebleeding of the aneurysm. 32 patients (57.1%) were treated with surgery or endovascular coiling. Seventeen patients (30.4%) have lost their opportunity of ultimate treatment because they had poor clinical course after extra-ventricular drainage. Final clinical outcome was not statistically different between early therapeutic group who underwent operation within 24 hours after extra-ventricular drainage and delayed therapeutic group who underwent operation after 24 hours. (Fisher extract test, survival rate P=0.603, clinical outcome P=1.000). CONCLUSION: Preoperative extra-ventricular drainage had additional risk of rebleeding, however, it provides immediate improvement of patient's neurological status and final clinical outcomes.