Hyperthyroidism is invariably accompanied by nervous system dysfunctions. Irritability, emotional lability and hyperkinesia are the signs and symptoms most frequently observed. Chorea or choreoathetosis are only rarely associated with hyperthyroidism. It is the purpose of this work to describe the case of a young girl in whom chorea was the main manifestation of thyrotoxicosis. The chorea receded and disappeared as the patient became euthyroid. Hyperthyroidism, therefore, is to be considered an unusual cause of chorea and every patient with choreiform movements should be examined also for thyroid function.