OBJECTIVE: The triad of acute spontaneous intracranial subarachnoid hemorrhage (SAH), hydrocephalus, and profound paraparesis in the absence of anterior cerebral artery vasospasm or ischemia has not been described previously. In this report, we present 6 patients presenting with this triad and provide a critical analysis of the clinical characteristics, radiographic workup, and long-term outcome for such patients. CLINICAL PRESENTATION: Six (0.9%) of 695 patients with nontraumatic SAH managed at Barnes-Jewish Hospital between January 2003 and January 2008 presented with profound paraparesis or paraplegia. All were Hunt and Hess Grade III or higher, and all had extensive SAH and ventriculomegaly on initial head computed tomography. Five patients underwent extensive spinal imaging, but no abnormality was identified. INTERVENTION: Five patients underwent surgical aneurysm obliteration, whereas 1 patient had no underlying aneurysm identified on multiple angiograms. All of the patients required urgent ventriculostomy for hydrocephalus, and 5 patients went on to require permanent shunt placement. Five of the 6 patients had gradual resolution of their presenting paraparesis over the course of 3 to 6 months. CONCLUSION: The clinical triad of SAH, hydrocephalus, and profound paraparesis has not been reported previously. In contrast to previous reports, these-patients had aneurysms at varying sites, without evidence of vasospasm or ischemia. Interestingly, all required acute cerebrospinal fluid diversion, 5 of 6 patients required permanent shunting, and almost all demonstrated gradual and often complete resolution of their presenting paraparesis. The etiology of this syndrome remains to be defined, but a combined deleterious effect of SAH and acute ventricular distention on cerebral function is suggested.