It has been proposed that mitochondrial dysfunction and excitotoxic mechanisms lead to oxidative damage in the brain of Huntington;s disease patients. We sought evidence that increased oxidative damage occurs by examining postmortem brain material from patients who had died with clinically and pathologically diagnosed Huntington's disease. Oxidative damage was measured using methods that have already demonstrated the presence of increased oxidative damage in Parkinson's disease, Alzheimer's disease, and senile dementia of the Lewy body type. No alterations in the levels of lipid peroxidation (as measured by lipid peroxides and thiobarbituric acid-malondialdehyde adducts) were found in the caudate nucleus, putamen, or frontal cortex of patients with Huntington's disease compared with normal controls. Similarly, there were no elevations in the levels of 8-hydroxyguanine or of a wide range of other markers of oxidative DNA damage. Levels of protein carbonyls in these tissues were also unaltered. Our data suggest that oxidative stress is not a major component of the degenerative processes occurring in Huntington's disease, or at least not to the extent that occurs in other neurodegenerative disorders.