The surgically treated 9 patients with anterior choroidal artery aneurysms were clinically analysed. The mean age of patients was fifty six and the size were between 3 mm and 12 mm. Anterior choroidal artery, although small, is important cerebral vessel because of its extensive strategic area of supply. We preserve anterior choroidal artery 8 out of 9 cases during clipping of aneurysm. Fortunately in the sacrificed case, no specific neurologic deficit was developed. So, we reviewed the anatomy & collateral circulation of this vessel.