Objective: To investigate the value of ultrasound detection of calcifications in differential diagnosis of benign and malignant thyroid nodules. Methods: The ultrasonographic data and clinicopathologic observations of 4 0 1 1 patients with thyroid disease undergoing surgical treatment from January 2005 to January 2010 were reviewed. The relations of whether or not calcification was present and different calcification patterns with benign and malignant thyroid nodules were analyzed, and the malignancy rate between single calcified nodule and multiple calcified nodules, and among calcified nodules of different ages groups were compared. Results: The malignancy rate in thyroid nodules with calcifications was significantly higher than that in those without calcification; in nodules with microcalcifications was signi?cantly higher than that with non-calci?cation; in single calcified or microcalcified nodule was significantly higher than in multiple calcified nodules; in calcified nodules in patients below 45 years old was significantly higher than that in those in patients greater than or equal to 45 years old, and all the difference had statistical significance (all P<0.05). For diagnosis of thyroid cancer, the sensitivity of calcification, microcalcification, macrocalcification and rim-like calcification was 80.42%, 51.65%, 26.52% and 2.25%, and their specificity was 67.53%, 93.19%, 76.79% and 97.55%, respectively. In the 39 patients with calcification in cervical lymph nodes, 37 cases were papillary thyroid carcinoma with lymph node metastases. Conclusion: Calcification and microcalcification in thyroid nodules has great importance in diagnosis of thyroid cancer. Single calcified nodule, microcalcified nodule, calcified nodules in patients younger than 45 years old, and calcification in lymph nodes have higher malignancy rate.