Nowadays, patients with Graves' hyperthyroidism are initially treated with methimazole or propylthiouracil. Several serious adverse reactions like agranulocytosis are caused by these drugs. Inorganic iodine decreases serum thyroid hormone concentrations in patients with Graves' hyperthyroidism without adverse reaction, but this effect usually continues only a limited time. However, a virtually complete remission or longstanding euthyroid state may be obtained with inorganic iodine therapy alone in patients with mild Graves' disease, who show small thyroid volume and low TRAb titers. Inorganic iodine therapy may become one of the treatment methods in the patients with mild Graves' hyperthyroidism.