Objective:To study the gene expression of sodium/iodide symporter(NIS) in both differentiated thyroid carcinoma(DTC)and correlated lymph nodes metastasis,and explore the relationship between NIS expression and DTC,and between NIS expression and the significance of radioactive iodine treatment for DTC. Methods:The expression of NIS in tissue specimens was evaluated by RT-PCR technique and immunohistochemistry. Results:The RT-PCR result showed that the expression of NIS mRNA didn’t have significant difference between tumor-adjacent tissues and DTC tissues. The NIS mRNA expression in metastatic lymph nodes were lower compared with tumor and tumor-adjacent tissues. The immunohistochemistry result showed that NIS positive ratio in DTC and correlated lymph nodes tissue didn’t have significant difference compared with that in normal thyroid,respectively. Conclusion:The NIS could be normally expressed,but NIS protein was mostly expressed in the cytoplasm rather than in the functional membrane,which has guiding significance for the radioiodine treatment of DTC.