Abstract: The classic therapy of metastatic well differented thyroid cancer is administration of ¹³¹I after subtotal thy-roectomy.The sodium/iodine symporter (NIS)mediates the active transport of iodine into thyroid cells,while the thy-roperoxidase (TPO)suppresses the out-flow of iodine from thyroid cells.As a result,a new potential approach has been develepted with co-transfection of NIS and TPO genes to thyroid cancer cells,which can enhance the results of radioio-dine.Retinoide is also useful to ¹³¹I therapy for it can induce non-differented thyroid cancer cells to well-differnted cells to increase radioiodine uptake.