Study Objective: To demonstrate the prevalence of endometriosis in the intrapelvic portion of the round ligaments of the uterus (RLUs) and to propose criteria for their excision. Design: Retrospective case series analysis of women undergoing laparoscopy for the treatment of deep infiltrating endometriosis (Canadian Task Force classification II-3). Setting: Tertiary referral hospital. Patients: We evaluated 174 patients who underwent laparoscopy for the treatment of deep infiltrating endometriosis (DIE) between April 2006 and May 2009. Interventions: All patients underwent laparoscopy for the treatment of DIE and had their RLUs removed when there was shortening, deviation, or thickening. After removal, the RLUs were sent for histopathologic analysis to verify the presence or absence of endometriosis. Measurements and Main Results:The prevalence of endometriosis in the RLUs and the association between the macro-scopic alterations and the anatomic pathology results were determined. After the identification of macroscopic alterations, 1 or both RLUs (for a total of 42) were removed from 27 of the 174 patients who underwent laparoscopy. The positive predictive value (PPV) of the macroscopic criteria proposed for endometriosis of the RLU was 83.3% (95% confidence interval [CI]572.1%–94.5%), with 35 positive RLUs out of the 42 that were excised. The prevalence of endometriosis of the RLU was 13.8% (95% CI58.7%–18.9%), with 24 patients having a positive histopathologic examination result for endometriosis. Conclusions: The prevalence of RLU endometriosis in patients with DIEwas 13.8%, which emphasizes that a rigorous eval-uation of this structure must be part of the routine surgical treatment of patients with endometriosis.