Ataxia refers to motor incoordination that is usually most prominent during movement or when a child is attempting to maintain a sitting posture. The first part of the review focuses on the anatomic localization of ataxia -both within the nervous system and without -using a combination of historical features and physical findings. The remainder of the review discusses etiological considerations that vary depending on the age group under consideration. In infancy, certain specific diseases, such as opsoclonus myoclonus ataxia syndrome, must receive special mention because the underlying disease process may be amenable to surgical intervention. In the toddler-and school-age groups, certain conditions (such as stroke and acute cerebellitis) require immediate recognition and imaging, whereas others (such as post-infectious ataxia and concussion) require close follow-up. Finally, mention must be made of diseases outside of the central nervous system that can present with ataxia, such as Guillain-Barré syndrome.T he word ataxia is derived from the Greek word ataktos, which means "lack of order." Ataxia is characterized by disturbances in the voluntary coordination of posture and movement. In children, it is most prominent during walking (the sine qua non being a staggering gait with impaired tandem), but it can also be present during sitting or standing, or when the child is performing movements of the arms, legs, or eyes.This review focuses on the etiology and diagnostic considerations for acute ataxia, which for the purposes of this discussion refers to ataxia with a symptom evolution time of less than 72 hours.