The relationship of dopamine receptor binding in the caudate nucleus and the putamen to neurological and neuropsychological functioning was examined in 21 patients with Huntington's disease (HD) and eight individuals at risk of developing Huntington's disease. A significant reduction in relative binding of [11C] 3-N-methylspiperone to the dopamine receptor was found in both the caudate and putamen of HD patients. Binding in the caudate was correlated only with tests of rapid coding and set alternation, while binding in the putamen was correlated only with duration of illness. The findings indicate that the well-described atrophic changes in the striatum of Huntington's disease patients are accompanied by receptor alterations. They also support previous animal and human studies indicating that the caudate nucleus plays a larger role in cognition than in motor functions.