Huntington's disease (HD), a dominantly inherited disorder of the nervous system, is usually manifest about middle age by dance-like movements. The disorder may occur in children, when epilepsy and rigidity may be the predominant signs. Degeneration of neurons occurs throughout the whole brain, but this is most marked in the basal ganglia. Neurochemical examination of postmortem brain frozen at the time of autopsy has been collected from patients dying with HD and compared with postmortem brain from psychotic patients and cases without neuropsychiatric disease. A number of alterations in neurotransmitters and their biosynthetic enzymes have been found. There are decreased concentrations of the neuroinhibitory transmitter gamma aminobutyric acid and this is associated with increased concentrations of dopamine and serotonin in the basal ganglia. In addition, there is decreased activity of glutamic acid decarboxylase, choline acetyltransferase, angiotensin-converting enzyme, as well as a decreased concentration of the neuropeptide substance P. Various pharmacologic agents have been tried based on the neurochemical alterations, but nothing has been found to be superior to the various neuroleptics in common use.