Transvaginal sonography (TVS) is a valuable primary imaging tool for the initial evaluation and management of endometriosis, a complex multifocal disease process with a varied spectrum of clinical and morphologic features that can substantially affect quality of life. The high accuracy of TVS for the detailed mapping of disease extent, an essential process for guiding treatment strategies, is well documented. The dynamic nature of US provides added value, revealing information that is not easily addressed with other imaging modalities. As recognized by the International Deep Endometriosis Analysis Consensus Group, a dedicated standardized protocol that is used by experienced and knowledgeable operators is necessary for a complete evaluation. The four components of a dedicated TVS protocol for evaluation of pelvic endometriosis are (a) evaluation of the uterus and adnexa, (b) dedicated search for deep infiltrating endometriosis, (c) assessment of the sliding sign, and (d) detection of sonographic soft markers. These components are described, and the multiple locations and US findings of endometriosis within the pelvis are reviewed, with emphasis on the unique features of US as an extension of the physical examination. In addition to enabling evaluation of the static findings of adenomyosis, endometrioma, hydrosalpinx, hematosalpinx, and hypoechoic nodules of deep infiltrating endometriosis, dynamic TVS enables assessment of pouch of Douglas obliteration, organ mobility, and site-specific tenderness, as well as tenderness-guided imaging. The benefits of implementing a dedicated TVS protocol in terms of improved patient care are also discussed. Online supplemental material is available for this article. ©RSNA, 2019.