Background and Purpose— Patients suspected of having aneurysmal subarachnoid hemorrhage (SAH) are initially evaluated with noncontrast head computed tomography. If the computed tomography is negative, but clinical concern for SAH is high, a lumbar puncture with cerebrospinal fluid analysis is typically performed. The purpose of this study was to evaluate the accuracy of cerebrospinal fluid xanthochromia and erythrocytosis for aneurysmal SAH. Methods— Medical records of all patients who underwent catheter angiography at Barnes Jewish Hospital between July 2002 and April 2012 for clinical suspicion of a ruptured brain aneurysm after a negative computed tomography scan and a lumbar puncture suspicious for SAH were reviewed. The cerebrospinal fluid analysis results, angiographic findings, and outcomes of each case were recorded. Results— Fifty-seven patients were identified. Two angiographic lesions were identified in patients with xanthochromia (2/24 patients, ie, 8.3%), both of which were confirmed to have ruptured. The diagnostic yield in patients with nonclearing erythrocytosis and no xanthochromia was 6.3% (1/16 patients), although this lesion was not considered the source of SAH. Conclusions— Catheter angiography should be performed in patients with computed tomography negative but suspicious lumbar puncture, particularly in the presence of xanthochromia. The benefit of angiography in patients with erythrocytosis only is unclear and deserves future study.