We present the case of a 9-year-old female with cerebral palsy and repeated episodes of ballism associated with antiphospholipid and anticardiolipin antibodies. She was treated unsuccessfully with varying medications, including neuroleptics, anticholinergics, antiepileptics, dopamine, dopamine agonists, and monoamine oxidase inhibitors. Intravenous immunoglobulin and corticosteroids led to resolution of the movements. We postulate an immune mechanism of disease for ballism associated with antiphospholipid and anticardiolipin antibodies.