[en] To investigate the Doppler ultrasonographic parameters of a carotid ultrasound (CUS) for the stenosis of the intracranial internal carotid artery (IICA). The authors evaluated 15 patients with normal extracranial ICA, the common carotid artery (CCA), and stenosis of IICA (patient group). The control group consisted of 22 patients with normal findings on a magnetic resonance angiography (control group). All subjects were subjected to a CUS, whereas subjects from the patient group underwent a cerebral angiography. The following parameters were investigated: peak systolic velocity (PSV) and end diastolic velocity (EDV) in ICA, PSV in CCA, resistive index (RI) in ICA, and PSV ratio. Stenosis was measured following an angiography and was graded as follows: normal (0-24%), mild (25-49%), moderate (50-69%), and severe (70-99%). Next, the CUS findings, which reflected the IICA stenosis, were investigated. Of the 74 ICAs, 52 were normal (44 ICAs in the normal group and 8 ICAs in the patient group), 10 had mild stenosis, 8 had moderate stenosis, and severe 4 had severe stenosis. As the stenosis grade increased, PSV and EDV in ICA as well as PSV in CCA, decreased (ρ value < 0.05); however, the PSV ratio and RI remained unchanged. As stenosis of IICA increases, PSV and EDV of ICA and PSV of CCA decreases following a CUS