In the last few years both neuropathological and neurochemical data have contributed towards a classification of the pathogenesis of degenerative chorea of which Huntington's chorea shows clear evidence of heredity. The role of GABA, DA and Ach in determining chorea seems clear. In 7 patients with degenerative hypotonic-hyperkinetic chorea (the acid metabolites into the cerebrospinal fluid are not available) a neuropharmacological study was conducted. The symptomatology was evaluated both through clinical rating and through phasic and tonic performance tests. The neuropharmacological tests were both acute and chronic. In the acute tests the effect of modification of various neurotransmitters (Ach, DA, NA, GABA) was evaluated. In chronic treatment the effectiveness of haloperidol, PCPA and bromocryptine was evaluated. The results of the acute study were positive both as regards increment of DA (receptors stimulation) and GABA. The chronic study shows any effect of PCPA, positive results both with bromocryptine and with haloperidol. Our results confirm a DA/GABA interaction in the pathogenesis of degenerative chorea.