Medullary thyroid carcinoma (MTC) originats from the parafollicular C cells of the thyroid, which is one of the most aggressive forms of thyroid malignancy with the poor prognosis. Hereditary MTC has multiple endocrine neoplasia types 1, 2A and 2B. The mutation of RET proto-oncogene has been identified as the main cause of MTC, and all mutations locate among the exons 5, 8, 10, 11, 13, 14, 15, and 16. Mutation analysis of the RET may provide a theoretical basis for the prevention, diagnosis and treatment of MTC.