Objective: To report the effects of noninvasive standard physical therapy (PT) interventions on an involuntary movement disorder after stroke. Design: Single case with clinical follow-up over 2 years. Setting: Inpatient stroke and rehabilitation services and outpatient clinic. Participant: A man with acute bilateral ballism after unilateral subthalamic infarction. Interventions: Rhythmic coordinated bilateral limb movements and firm tactile stimulation to the hand. Main Outcome Measures: We had not anticipated that dyskinesia itself would specifically improve during treatment. Consequently, we used qualitative clinical observations, including review of videotaped performance, and self-reported limb control. Hypotheses concerning treatment effects were developed after data collection. Results: Involuntary movements recurrently improved within treatment sessions. Conclusions: PT may improve dyskinesia after stroke. The benefit may be adjunctive or alternative to current invasive treatments of movement disorders after brain injury and merits confirmation. The improvements are consistent with current research indicating that (1) intact cortical, subcortical, cerebellar, and spinal areas interact to generate bilateral rhythmic limb movements that can overcome dyskinesia and (2) tactile stimulation can improve motor deficits associated with basal ganglia disorders. Finally, because functional activities assessments improved our evaluation of ballism, these should be routinely used along with conventional neurologic examination to assess involuntary movement disorders. © 2005 by American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.