OBJECTIVE: The goal of this study was to document the influence of the treatment method (early surgery versus early endovascular treatment) on the development of chronic shunt-dependent hydrocephalus in a series of 242 patients treated within 7 days after aneurysmal subarachnoid hemorrhage (SAH). METHODS: The following parameters were prospectively recorded in a computerized database and retrospectively analyzed for association with chronic shunt-dependent hydrocephalus: 1) Hunt and Hess grade, 2) Fisher computed tomographic grade, 3) incidence of repeat SAH, 4) aneurysm location, and 5) treatment method (early surgery versus early endovascular treatment). RESULTS: Forty of 187 patients (21.4%) who survived the SAH and its neurological and/or medical sequelae underwent definitive shunting for treatment of chronic hydrocephalus. The rate of shunt dependency was positively correlated with a higher Hunt and Hess grade (P < 0.001), a higher Fisher computed tomographic grade (P = 0.003), the occurrence of intraventricular hemorrhage (P < 0.001), repeat SAH (P = 0.003), and aneurysms arising at the anterior communicating artery (P < 0.001). CONCLUSION: The results of the present study indicate that the treatment method used does not affect the risk of the later development of chronic shunt-dependent hydrocephalus (early surgery, 23.2% [29 of 125]; early endovascular treatment, 17.7% [11 of 62]; P = 0.45).