trans-Dihydrolisuride, a partial dopamine receptor agonist, was tested for its effects on chorea in a double-blind, crossover clinical study in 10 patients with Huntington's disease. In eight patients, a neurophysiological evaluation was also performed. No reduction in choreic movements or improvement in voluntary movement performance was observed. However, in some patients, there was a slight improvement in patients' alertness and a reduction of the movement reaction time.