One of the major complications during or after percutaneous transluminal angioplasty (PTA) is distal embolism. We performed intravascular ultrasound (IVUS) to assess the morphological characteristics of atheromatous plaques which caused stenosis of arteries. In 7 cases of ICA stenosis, IVUS demonstrated hyperechoic plaques which were considered to be fibrous. Mixed type of plaque was observed in one case of ICA stenosis and another one case of ICA stenosis had plaque which was hyperechoic with acoustic shadowing. In all cases of SCA stenosis, plaques were hypoechoic, indicating fatty plaque. Distal embolism occurred after PTA in the case of ICA stenosis which had a mixed type of plaque. It is important to evaluate plaque morphology to prevent distal embolism. PTA is considered to be contraindicated in cases of ICA stenosis having hypoechoic plaques or ulceration.