Neurotransmitter-receptor binding sites for apparent muscarinic cholinergic, beta-adrenergic, gamma-aminobutyric acid and serotonin receptors were measured in the caudate nucleus and frontal cerebral cortex from post-mortem brains of 16 patients with Huntington's chorea and 16 controls. In addition, the samples were assayed for the gamma-aminobutyric-acid-synthesizing enzyme, glutamic acid decarboxylase, and for the acetylcholine-synthesizing enzyme, choline acetyltransferase. In the caudate nucleus of choreic brain, both enzyme activities were markedly lower, with significant decreases in muscarinic cholinergic and serotonin receptor binding, whereas enzyme activities and receptor binding were unchanged in the cerebral cortex. By contrast, gamma-aminobutyric acid and beta-adrenergic receptor binding were not significantly different in choreic and control caudate nucleus or cortex, suggesting that, despite the loss of gamma-aminobutyric-acid-synthesizing ability in the corpus striatum, gamma-aminobuytric acid mimetic drugs might alleviate the movement disorders in Huntington's chorea.