Purpose : To assess the usefulness of CT angiography(CTA) compared with compared with conventionalangiography(CA) in the evaluation of intracranial occlusive vascular disease. Materials and Methods : We evaluated26 patients with clinically suspected intracranial occlusive vascular disease studied with both CTA and CA. Incases where there was no vascular lesion on CA, we used CTA to retrospectively review the detection rate and sizeof individual vessels, and compared the findings with those obtained by CA. In cases of occlusive vascular lesion,we evaluated the degree of stenosis on CTA and compared this with the CA findings. We also measured the time takento use both modalities. Results : Sixteen patients had no vascular lesion and ten patients had occlusive vascularlesions. Compared with CA, CTA detected 97%(124/128) of normal intracranial arteies ; their diameter measured onCTA was slightly smaller than that on CA. On CTA, the degree of stenosis was correctly estimated in eight lesions,underestimated in one and overestimated in one. Examination time ranged between 15 and 20 minutes with CTA andbetween 40 and 60 minutes with CA. Conclusion : Compared with CA, CTA shows good correlation in the delineation ofintracranial normal and occlusive vessels around the Circle of Willis. CTA may be an additional tool for theevaluation of the Circle of Willis in patients with suspected intracranial occlusive vascular disease. CTA may,additionally, be used as a follow-up method in patients with acute cerebral infarctions after thrombolytictherapy.