The aim of this study was to investigate the long-term natural history of nontraumatic angiogram-negative subarachnoid hemorrhage with typical pretruncal (P-SAH) and diffuse (D-SAH) pattern of hemorrhage. A retrospective review of 102 patients who experienced angiographically negative SAH at our institution was undertaken (11.6% of 882 spontaneous SAH). Follow-ups were obtained at 7.9 to 16 years. In the D-SAH group, 11 patients (13.9%) out of 79 had an aneurysm, and four (5.1%) had rebleeding episodes. In the P-SAH group, the second angiography was negative in all of the 23 cases, and no rebleeding episodes were recorded. The long-term follow-up confirms that P-SAH is a benign disease. A second angiography could not be necessary. D-SAH is probably due to an aneurysm that thrombose early after the bleeding. At short-term follow-up, the sack could frequently recanalize and rebleed, whereas a late follow-up shows that rebleeding is very rare.