Malignant cells demonstrate increased glucose uptake and utilization. Immunohistochemical studies have suggested that enhanced glucose uptake in cancer cells may be caused by the overexpression of glucose transporters (GLUTs), in most cases GLUT1 and/or GLUT3. The aim of this study was to examine in detail the expression pattern and levels of GLUT genes in normal and pathologic thyroid tissues and to evaluate the clinical significance of GLUT mRNA levels. One hundred fifty-two surgically resected thyroid tissue samples from 103 patients were evaluated. Samples included: normal thyroid tissue (n = 58), benign thyroid disease (n = 61), and thyroid carcinoma (n = 33). Expression of the GLUT1, GLUT2, GLUT3, GLUT4, and GLUT10 genes were examined by reverse transcription-polymerase chain reaction (RT-PCR) and mRNA levels were quantitated by real-time RT-PCR. All thyroid parenchymal cells expressed GLUT1, GLUT3, GLUT4, and GLUT10. GLUT1 showed increased expression in carcinoma cases (p < 0.0001) and also in comparison with paired normal tissue samples from the same patient (p < 0.0001). Other GLUTs were statistically unchanged in pathologic tissues. These results are consistent with the theory that GLUT1 is upregulated during carcinogenesis and may play a major role in enhanced glucose uptake in thyroid cancer cells.