Objective: The incidence of subarachnoid hemorrhage (SAH) in the young is increasing recently. Among the young patients, some of them do not have detectable aneurysms, so the cause of the disease may be non-aneurysmal. in this study, we analyzed some clinical cases of subarachnoid hemorrhage in young adults and discussed the possible causes other than present aneurysm and arteriovenous malformation (AVM). Methods: We reviewed 11 patients with SAH below 45 years of age enrolled in our hospital from January 2007 to June 2008. Their clinical characteristics, imaging examination results were analyzed in details: nine patients were found with no obvious cause for their hemorrhage. Four of them were followed up for 1 year and the other three were followed up for half a year. We telephoned the seven patients to gain the information on their recovery by questionnaire. Results: With an average onset age of 38 years old, all patients had similar symptoms and onset behavior according to their clinical characteristics. Based on the imaging results, two had confirmed vascular malformation; the other nine did not present detectable aneurysm or AVM, but with different morphological changes of their cerebral arteries. By 1-year or half-year follow-up, the seven patients were found to have good recovery. Conclusion: Pathological changes of cerebral vessels due to smoking, genetic, or as an early version of formation of aneurysm, might be contributed to SAH in the young. Repeated angiogram is necessary for young patients to confirm the cause of SAH.