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.