BACKGROUND: We examine two accepted methods of managing cerebrospinal fluid (CSF) drainage in patients following subarachnoid hemorrhage (SAH). The first is intermittent CSF drainage when intracranial pressure (ICP) reaches a pre-defined threshold (monitor-first) and the second is continuous CSF drainage (drain-first) at set pressure thresholds. This pilot study is designed to determine if there is a cause for a randomized study of comparing the two methods. METHODS: This prospective observational pilot study enrolled 37 patients with SAH and external ventricular drainage between October 2008 and August 2009. Patients were treated with one of two methods of ICP management (drain-first vs. monitor-first) according to the discretion of the admitting physician. RESULTS: There were no significant differences in baseline characteristics including age, gender, severity of neurological dysfunction, and radiographic findings between the two groups. The incidence of vasospasm was not different between the drain-first group (66.7%; 16 of 24 patients) and the monitor-first group (53.9%; 7 of 13 patients). CONCLUSION: This pilot study was neither powered, nor expected to detect a difference between groups. The results of this study provide support for the design and conduct of a randomized study to assess the impact of two methods of CSF diversion for patients with SAH.