Endometriosis is a common condition, but its exclusive localization on the ileum is very rare. Unless there is catamenial exacerbation of symptoms, and considering the lack of specificity of results, diagnosis can be difficult. We report the case of a 50 year-old woman presenting with chronic pain in the right lower quadrant. Initial explorations revealed an ileal tumor which was not characterized before the occurrence of acute small bowel obstruction. Ileo-caecal resection by laparotomy relieved the symptoms and alllesions were removed. Diagnosis of ileal endometriosis was made by pathological examination of the resected specimen.