In recent years, ultrasound scanning has become an important diagnostic tool in dermatology. It is easy to use, completely safe, and provides important diagnostic information. There are 2 basic types of ultrasonography with dermatologic applications. The best established is 20-MHz scanning, which can be used to measure tumor thickness and/or skin thickness when treating inflammatory diseases such as scleroderma or psoriasis. Real-time sonography with 7.5- to 10-MHz probes has assumed an increasingly important role, since it is used to search for and image lymph nodes and subcutaneous tumors in a variety of clinical settings, including preoperative staging and follow-up of melanoma. Ultrasonography is capable of revealing the 3-dimensional size and outline of subcutaneous lesions, for example, lymph nodes, subcutaneous tumor masses or hematomas, and their relation to adjacent vessels. Moreover, information about the lesion quality (solid, cystic, and combined) and the inner structure (homogeneous, inhomogeneous, hypoechoic, hyperechoic, calcification foci, and necroses) can be obtained. All this information can be combined to help distinguish between benign and malignant lymphadenopathy and to determine the malignant potential of a subcutaneous lesion. In addition to conventional B-mode sonography, newer ultrasound techniques such as native and signal-enhanced color Doppler sonography can be used to assess peripheral lymph nodes.