Cerebral pan-angiography was repeated in 24 patients with spontaneous subarachnoid hemorrhage confirmed by spinal fluid or computed tomography evidence after the initial pan-angiography was negative. Recent, long-term follow-up was also conducted. The pan-angiography was technically adequate and did not show vasospasm, both being causes of aneurysmal nonvisualization. No etiology was demonstrated on repeat study in all 24 patients. An additional three patients had only one study, but autopsy later confirmed lack of etiology for subarachnoid hemorrhage despite gross and microscopic serial sections. The mean duration of follow-up was 18.1 years and outcome was favorable. Our results suggest that repeat cerebral pan-angiography may not be indicated in the patient who has no further bleeding episodes and in whom the initial study was normal, technically adequate, and complete without evidence of vasospasm. Nonvisualization of a cerebral aneurysm is commonly proposed as the most likely cause of subarachnoid hemorrhage when angiography is normal following nontraumatic subarachnoid hemorrhage. Our results suggest this conclusion is no longer accurate if the angiogram is technically adequate with the absence of vasospasm.