We present a 15-year-old girl with an unusual clinical course of intractable thyrotoxicosis that was resistant to thiocarbamide therapy and propranolol. Although the latter beta-adrenergic blocking agent has been used as the sole drug in the preparation of thyrotoxicosis patients for thyroidectomy, it was unsatisfactory for control of our case. In contrast, the patient's clinical response to lithium carbonate 900-1500 mg/d for 10 days was very good and no side effects were observed. This demonstrates the importance of lithium as the drug of choice in thyrotoxic emergencies and uncontrolled preoperative patients when rapid and safe inhibition of thyroid hormone secretion is required.