The sonograms and medical records of 49 patients were reviewed to determine if there is a characteristic sonographic appearance for certain neck masses. Neck masses included: inflammatory masses (12), noninflammatory masses (23), and thyroid masses (14). Four entities including thyroglossal duct cyst, fibromatosis colli, cystic hygroma, and multiple lymphadenopathy showed characteristic sonographic appearance. Thyroglossal duct cysts were seen as midline or slightly off midline cystic masses. A sinus tract extending superiorly was nicely demonstrated in one patient. The mass in fibromatosis colli (neonatal torticollis) appeared as a well defined mass clearly within the sternocleidomastoid muscle, uniformly echogenic, but less echogenic than the normal surrounding muscle, without good through-transmission. A cystic or primarily cystic mass with linear septations was the characteristic finding of the cystic hygroma. Multiple lymphadenopathy demonstrated multiple discrete, oval, relatively hypoechoic masses along the cervical lymphatic chain. The sonographic appearance of inflammatory masses was variable, being either inhomogeneously echogenic or of mixed echogenicity. Hemangiomas were either echogenic with cystic vascular spaces or linear septations or relatively homogeneously echogenic. Intrinsic thyroid masses could be distinguished from extrinsic masses in most cases. The demonstration of calcification in a mass was useful in narrowing the differential diagnosis. Although it is not a specific finding, the presence of calcification highly suggests a neoplastic lesion, particularly neuroblastoma or teratoma. Not only can the location, extent, and internal characteristics of a mass be determined, but in certain entities, the sonographic appearance is characteristic and an accurate diagnosis can be made.