We report the treatment of four thyrotoxic patients. Two were cases of type I 
amiodarone-induced thyrotoxicosis (AIT) treated with methimazole. The third 
Graves' disease patient, who became hypothyroid 25 years after subtotal 
thyroidectomy, developed type II AIT. Furthermore, one case with heart failure 
and ventricular tachycardia, who developed an adverse reaction to antithyroid 
agents and was prescribed amiodarone, underwent total thyroidectomy. The 
clinical course was uneventful, and the patient is doing well. Since amiodarone 
contains a large amount of iodine, it is frequently difficult to make a 
differential diagnosis. Surgical treatment of Graves' disease patients is 
recommended when immediate control of hyperthyroidism and heart failure is 
required.