Ultrasonography (US) with a high-frequency (7.5-10-MHz) transducer has become the imaging modality of choice for examination of the scrotum. US examination can provide information valuable for the differential diagnosis of a variety of disease processes involving the scrotum that have similar clinical manifestations (eg, pain, swelling, or presence of mass). The pathologic condition that may be at the origin of such symptoms can vary from testicular torsion to infection to malignancy. The ability of color and power Doppler US to demonstrate testicular perfusion aids in reaching a specific diagnosis in patients with acute scrotal pain. This review covers the anatomy of the scrotum and the scanning protocol for scrotal US, as well as detailed descriptions of disease processes and their US appearances. Newly described conditions such as intratesticular varicoceles and other benign intratesticular cystic lesions are also discussed.