Ataxia, a neurological sign characterized by the incoordination of voluntary movements, is the most prominent manifestation of cerebellar disease. The cardinal features of cerebellar dysfunction involve disturbances of stance, gait, eye movements, muscle tone, skilled movements, and speech. Classification and differential diagnosis of ataxic syndromes have intrinsic complexity owing to the variability in phenotypic presentations and in etiologies, which include trauma, toxic and metabolic causes, neoplasms, immune mechanisms, and genetic diseases. Pure cerebellar symptoms are rarely observed, while the clinical picture of both genetic and sporadic ataxia syndromes is sometimes complicated by the presence of extracerebellar neurological or multisystem extraneural pathology. Clinical presentation and assessment of the patients together with classification, genetic aspects, and principles in differential diagnosis of ataxias are briefly reviewed.