The most important roles of ultrasound in breast imaging include the diagnosis of cysts and the characterization of masses that have been incompletely assessed by mammography. Ultrasonography techniques such as harmonic and compound imaging have recently been introduced and are more efficient than conventional imaging in terms of lesion conspicuity and the characterization of breast nodule. The BI-RADS classification is an important system for describing and classifying breast lesions. With this approach, a population of benign solid breast lesions that does not require biopsy can be accurately defined. Ultrasonography should be performed as first-line examination in juvenile, in pregnant women and in patients with inflammatory syndrome. Ultrasound can detect mammographically occult breast the way they develop.