We report carotid ultrasonographic findings in moyamoya disease. A 44-year-old man was admitted to our hospital because of fever, headache and nausea. Neurological examination showed neck stiffness and Kernig's sign but he was otherwise normal. Brain computed tomography showed hemorrhage in the right thalamus and the lateral ventricle. Conventional carotid ultrasonography (CCU) detected marked narrowing of the right internal carotid artery (ICA) at the proximal portion without arteriosclerosis, which fulfilled the criteria of bottle neck sign, namely, the ratio of diameter of proximal portion of ICA to that of the distal portion of common carotid artery (CCA) was less than 0.5. Additionally, CCU as well as transoral carotid ultrasonography (TOCU) showed the diameter of the ICA to be smaller than that of the external carotid artery (ECA) (diameter reversal sign). These signs strongly suggested moyamoya disease. Cerebral angiography confirmed the occlusions of intracranial ICA and moyamoya vessels. Bottle neck sign and diameter reversal sign of the carotid artery on carotid ultrasonography are useful for the early detection of moyamoya disease.