The existence of the natriuric/iodide symporter (NIS) represents a new view to understand the thyroid metabolism of iodide. Due to its cellular localisation on basolateral membrane, this transporter exerts an essential role in the biological functions of the thyroid, especially the capacity to accumulate iodide into the thyrocytes. Clinical perspectives of NIS activity modulation would ameliorate the diagnosis and the treatment of thyroid diseases by using radioisotopes transported by the NIS (131 iodide, 99m technetium, 188 rhenium). The study of the regulation pathways modulating the expression and the activity of the symporter NIS, would allow to understand pathogeny of benign or malignant diseases of the thyroid gland. The relative facility of the therapy management by 131 iodide and its good efficiency associated to the recent advance of NIS function also give an interesting perspective to the gene therapy treatment of the nonthyroid cancers despite existent methodological problems.