The ability of the selective GABA-receptor agonist, progabide, to suppress abnormal involuntary movements was evaluated in a preliminary open pilot study. 17 patients, 10 males and 7 females, aged 10-78 years, with hyperkinetic movement disorders were included in the study. Daily doses of progabide ranged from 900 to 3600 mg (median 2400 mg) corresponding to 14-45 mg/kg (median 45 mg/kg), while the duration of treatment varied from 2 to 52 weeks. Improvement, with a reduction of involuntary movements exceeding 25%, occurred in two of four patients with Gilles de la Tourette's syndrome, and in two of three patients with postanoxic intention myoclonus, while no consistent beneficial effects were registered in ten patients with Huntington's chorea, postanoxic choreoathetosis, torsion dystonia, tardive dyskinesia, action tremor, essential myoclonus, or oro-branchio-respiratory myoclonus.