Deep infiltrating endometriosis (DIE) is described as an endometriotic tissue that penetrates more than 5 mm under the peritoneal surface. It's suggested that trans vaginal sonography (TVS) is 79% sensitive and 94% specific in the assessment of intestinal DIE. Considering the possibility that DIE ultrasonography (rectal and\or vaginal ultrasonography) might be more accurate, we designed this study to assess this study to evaluate the accuracy of DIE ultrasonography. In this retrospective cross-sectional study, we designed and conducted this study from 2019 to 2020 on patients suspected of severe endometriosis. Our patients underwent ultrasonographic imaging and based on the results became candidates for surgery. We compared histopathological results with sonographic findings using crosstabulation and chi-square tests were used to measure accuracy. P<0.05 were considered statistically significant. Following pathological assessments of 109 cases, 97 cases had ovarian endometrioma, 42 cases had intestinal involvement and 56 cases had uterosacral DIE. The results for accuracy were as the following; uterosacral ligament (USL) involvement SE: 96.4% and SP: 59.1%; intestinal involvement SE: 97.6% and SP: 73.8%; and Cul de sac involvement with SE: 100% and SP: 50.8%. With regards to ovarian endometrioma, ultrasonographic imaging was 99.0% sensitive and 84.6% specific. With regards to intestinal involvement, ultrasonography performed a reliable overall diagnosis (97.6% sensitive and 73.8% specific). However, the results showed lower accuracy regarding the level of intestinal involvement. The accuracy for other sites and cavities was low except for ovarian endometrioma. The results of the present study demonstrated that pre-operative TVS and Transrectal ultrasound (TRUS) can be a helpful paraclinical tool in the assessment and diagnosis of DIE and endometriosis in general and particularly with adnexal and bowel lesions, it can have some shortcomings with respect to cul de sac and USLs.