Objective To investigate the expression of sodium iodide symporter (NIS ) mRNA in differentiated thyroid Carcinoma (DTC)and further explore its value in clinical diagnosis and therapy of DTC. Methods The expression of NIS mRNA was detected and analyzed in 21 nodular goiter and 45 cases of DTC (including 35 cases of papillary thyroid carcinoma and 10 cases of follicular thyroid carcinoma)by using real-time fluorescent quantitative reverse transcription polymerase chain reaction (real-time RT-PCR).Results Compared with that in nodular goiter,the mRNA expression of NIS in DTC tissue was significantly decreased (P < 0.05 ). Moreover,the mRNA expression of NIS was significantly correlated with lymph node metastasis and AJCC stage, respectively.The expression of NIS mRNA in DTC with lymph node metastasis was significantly decreased compared with that in DTC without lymph node metastasis (P <0.05).In addition,the expression of NIS mRNA in Ⅱ-Ⅳstage DTC was significantly decreased compared with that in Ⅰ - Ⅱ stage DTC (P < 0.05 ).Conclusion Differential expression of NIS can provide evidence for individual 1 3 1 I therapy for DTC.