Agenesis, aplasia and hypoplasia of the internal carotid artery (ICA) are rare congenital anomalies, occurring in less than 0.01% of the population. We report a case of ICA hypoplasia. A 47-year-old female visited emergency room complaining of dizziness. On the neurologic examinations, there were no abnormal findings. MR angiography showed diffuse narrowing of right ICA with occlusion at cavernous segment. The axial image of brain CT angiography showed asymmetrically small right carotid canal. She was diagnosed as hypoplasia of ICA. Journal of Neurosonology 8(2):49-51, 2016 Key Words: Internal carotid artery hypoplasia, Carotid canal hypoplasia, MR angiography