Aim: To regulate the diagnostic performance of specific ultrasound features to distinguish endometriomas from other adnexal masses. Study design: A retrospective study. Place and Duration: In the Obstetrics & Gynecology Unit II of Services Hospital Lahore for one-year duration from March 2018 to March 2019. Methods: The study was held among 65 patients who attended the Infertility Center. Infertile women> 25 years old, patients undergoing laparotomy or laparoscopy were included in the study. Patients with ectopic pregnancy and pelvic inflammatory disease were excluded. All patients were prospectively evaluated by vaginal examination. Ultrasound criteria for diagnosing endometrioma are round shape, low-level diffuse internal echoes, cystic structure in the adnexa, multilocularity, hyperechoic focal walls and wall thickness. Results: Histopathological findings of adnexal mass are endometrioma in forty cases, dermoid cyst (n = 3), malignant tumor (n = 2), hemorrhagic cyst (n = 6) and benign cyst. Benign torsional cysts of the ovaries n = 1, broad ligament hematoma n = 1, paraplegic cyst n = 1, hydrosalpinx n = 1 and a single functional cyst n = 7, the results were statistically analyzed and sensitivity determined. specificity of TVS with diagnosed endometrioma was 90%, sensitivity was 86%; 91% was PPV and 98% negative predictive value. Conclusion: Adnexal mass with low diffuse internal echoes and no specific tumor features is highly advanced in the case of endometriomas if there are multilocularity/hyper echoic wall foci present. Keywords: TVS, endometrioma, adnexal mass.