Over the past 15 years the use of transcranial B-mode sonography to assess brainstem and subcortical brain structures has become an important tool for the diagnosis and differential diagnosis of various movement disorders. The most widely recognised finding for movement disorders has been an increase in echogenicity of the substantia nigra, an area of the midbrain that is affected in idiopathic Parkinson's disease (PD). This finding has enabled the reliable diagnosis of PD with high predictive values. Other sonographic features, such as hypoechogenicity of the brainstem midline and hyperechogenicity of the lentiform nucleus, might help the differential diagnosis of PD and other movement disorders. This Review provides detailed information about the advantages and limitations of this novel neuroimaging method, including guidelines for the scanning procedure and considerations on the origin of ultrasound abnormalities. We discuss the use of transcranial sonography for early and preclinical diagnosis and for differential diagnosis of PD and other movement disorders, and we compare this method with other functional neuroimaging strategies. Transcranial B-mode sonography is a reliable, non-invasive, commonly available, easily applicable, and inexpensive method, which provides new information about the morphology of the brain to help the diagnosis of various movement disorders. Thus, this neuroimaging method could be recommended for general application in the diagnosis and differential diagnosis of PD.