Athetosis is a peculiar involuntary movement resulting from pathologic involvement of the basal ganglia. Although mechanism of this movement is still far from established, athetosis is clinically differentiated from chorea and dystonia. The purpose of this article is to review and summarise the classification of this involuntary movement disorder. This movement disorder is classified into double athetosis, chorea-athetosis, unilateral athetosis and pseudo-athetosis. The double athetosis is featured by increased muscle tonus and irregular small amplitude movement, which appears the most frequently in patients of cerebral palsy. In chorea-athetosis, irregular abnormal movement is more prominent and larger than double athetosis. This type of movement appears commonly in patients other than cerebral palsy. Unilateral and pseudo-athetosis are derived not from disturbance of the basal ganglia but from impared sensory pathways of the deep sensation due to cerebro-vascular lesion. Stereotactic VL-thalamotomy is effective to relieve increased muscle tonus but not to decrease involuntary movement.