Ataxia is a common neurologic finding in many disease processes of the nervous system, and has classically been associated with numerous metabolic disorders. An error of metabolism should be considered when the ataxia is either intermittent or progressive. Acute exacerbation or worsening after high protein ingestion, concurrent febrile illness, or other physical stress is also suggestive. A positive family history can be an important diagnostic clue. Progressive molecular and biochemical techniques are revolutionizing this area of medicine, and there has been rapid advancement in understanding of the disease processes.