Authors retrospectively analysed 45 US of 43 patients with surgically proved thyroid nodules. Ultrasonographic study was useful for detection and localization of thyroid nodules. The results were as follows : 1. The incidence was predominent in female (M : F ≒ 1 : 4 ). 2. Follicular adenomas were composed of 6 cases of cystic, 10 of solid and 12 of complex nodule. especially, well defined, anechoic mass or homogeneously solid nodule with complete peripheral halo was suggestive of the follicular adenomas. 3. Nodular hyperplasia were composed of 2 cases of cystic and 6 of complex nodule. The most common sonographic finding of the nodular hyperplasia was irregularly marginated, multiseptated complex mass with partial peripheral halo. 4.Adenocarcinomas were composed of 4 cases of solid and 5 of complex nodule. III defined, complex mass with irregularly marginated papillary intramural node and punctated calcification was suggestive of the adenocarcinoma. Especially, cervical lymphn de enlargement is an important role for the diagnosis of the adenocarcinoma.