Five female patients with idiopathic torsion dystonia (ITD) responded to treatment with tiapride, a selective D-2 dopamine antagonist. Previous treatments with various drugs, including anticholinergics, were ineffective. It is suggested that the previously reported genetic subgroups of ITD respond to different drug regimens. The autosomal dominant group responded to anticholinergics, while the autosomal recessive group responded best to a selective D-2 dopamine antagonist.