Objective:To evaluate of value of 64-slices spiral CT angiography(CTA)in the etiological diagnsis of subarachnoid haemorrhage(SAH).Methods:CTA was performed in 89 cases with spontaneous SAH admitted from September 2005 to September 2006

49 of whom also underwent digital subtracted angiography(DSA).The findings of CTA were compared with the results of DSA.Results:Among the 89 patients

CTA revealed 69 cases with cerebral aneurysm

9 arteriovenous malforma- tion(AVM)

2 thrombus of venous sinues

8 negative findings.Among the 49 patients who underwent both CTA and DSA

all but 1 lesions showed by CTA

either cerebral aneurysms(n=41)or AVMs(n=4)

were confirmed by DSA.DSA failed to show one case of small anterior communicating aneurysm demonstrated by CTA.It was found that CTA sensitivity and specificity was 100% and that DSA sensitivity was 98% and specificity was 100% in diagnosis of intracranial aneurysms in etiological diagnosis of SAH.Conclusion:64-slices spiral CTA is a non-invaise

fast convenience imaging modality for etiological diag- nosis of the SAH and also play an important role in selecting therapy and assessing difficulties of treatment.