Aceruloplasminemia is characterized by iron accumulation in the brain as well as in visceral organs, due to the absence of ceruloplasmin ferroxidase activity. The neurological symptoms, which include involuntary movements, ataxia, and dementia, reflect the sites of iron deposition. The unique involvement of the central nervous system distinguishes aceruloplasminemia from other inherited and acquired iron storage disorders. Excess iron functions as a potent catalyst of biologic oxidation. An increased iron concentration was associated with increased lipid peroxidation in the brains of three aceruloplasminemia patients. Positron emission tomography showed brain glucose and oxygen hypometabolism. Enzyme activities in the mitochondrial respiratory chain of the basal ganglia were reduced to about 50 and 43%, respectively, for complexes I and IV. Those of the cerebral and cerebellar cortices also were decreased approximately 62 and 65%. These findings suggest that iron-mediated free radicals may contribute to neuronal cell damage through increased lipid peroxidation and the impairment of mitochondrial energy metabolism in aceruloplasminemia brains.