The neuropsychiatric manifestations of systemic lupus erythematosus (SLE) are diverse but, among them, movement disorders are distinctly uncommon. We describe a 30-year-old female with SLE who developed sudden onset of right-sided hemiballismus. Previous cerebral venous thrombosis and a poor obstetric history suggested the antiphospholipid syndrome but only minimally elevated levels of anticardiolipin antibodies were detected. The underlying pathology could not be established but was most likely to have been a microinfarct of the contralateral subthalamic nucleus. Our patient responded rapidly to haloperidol alone without the requirement for corticosteroids.