We report four cases of life-threatening amiodarone iodine-induced thyrotoxicosis. Two patients died of a thyroid storm, and the other two patients developed severe thyrocardiac disease unresponsive to 6 months intensive antithyroid and steroid therapy. One of these latter patients died 1 month after thyroidectomy. Euthyroidism was achieved in the last patient by treatment with potassium perchlorate. The course could not be explained by the prior thyroid or cardiac status in any of the four cases.