Benign hereditary chorea (BHC) is an autosomal dominant disorder characterized by chorea of early onset with little or no progression. There is marked clinical variability in this disease with some subjects having onset in infancy and others with onset in early adulthood. In contrast to Huntington's disease (HD), there is no dementia. Computed tomography is normal in all subjects with no evidence of caudate nucleus atrophy. We present the results of positron emission tomography using 18F-2-fluorodeoxyglucose on three patients with this disorder from two families. Cerebral glucose metabolism in one patient was decreased in the caudate nucleus, as previously reported in HD. The other two persons from a second family showed a relative decrease in metabolic rates of glucose in the caudate when compared with the thalamus. It appears that caudate hypometabolism is not specific for HD. These findings suggest that the caudate nucleus may play a significant role in the pathophysiology of some persons with BHC.