We examined 106 members of a family affected with dopa-responsive dystonia (DRD), a subset of idiopathic dystonia. Ten members had unequivocal dystonia; 8 of these had generalized dystonia and the other 2 had focal dystonias (writer's cramp and spastic dysphonia). Twenty members had lesser dystonic signs and symptoms suggestive of a diagnosis of dystonia. Five members, including 1 with dystonia, had prominent parkinsonism that became symptomatic in late adulthood. All members affected with dystonia or parkinsonism had increased muscle tone (rigidity), which may represent the minimal clinical expression of DRD. Gene penetrance in families with DRD may be greater than previously suspected.