Ultrasonography is used primarily in the diagnostic workup of patients with pelvic pain or subfertility. It allows a detailed and dynamic evaluation of the pelvis to determine the presence or absence of endometriosis lesions or other possible reasons for the symptoms. A gentle approach in a reassuring environment is essential both for minimizing patients’ discomfort and optimizing the diagnostic yield. The sonographic examination is performed mainly via transvaginal scanning and covers the anterior compartment (e.g., the bladder wall and uterovaginal fold), the posterior compartment (e.g., the rectovaginal septum, uterosacral ligaments, rectosigmoid, and pouch of Douglas), the lateral pelvic compartment (e.g., the ureters and pelvic sidewalls), the ovaries (e.g., endometrioma), the uterus (e.g., adenomyosis), and other possible locations of endometriosis (e.g., the abdominal wall). The systematic ultrasound report should provide enough relevant information for the patient, the clinician, and the surgeon to decide on further management.