Since 1993, the American College of Radiology (ACR) has been publishing a BI-RADS "Breast Imaging-Reporting and Data System" for the accurate description of mammographic abnormalities. An ultrasound BI-RADS lexicon was developed in 2003, at the same time as the 4th edition of the mammographic BI-RADS, to standardize the characterization of ultrasound lesions, resulting in the most reproducible classification possible and appropriate management. The latest American version of BI-RADS was published by the ACR in 2013.In this pedagogical book, each term in the BI-RADS ultrasound lexicon will be explained in detail, with the help of rich iconography, leading us to the BI-RADS classification of lesions. This book will be of interest to all practicing physicians.