OBJECTIVE: To report a case of acute hemoperitoneum due to erosion of the uterine artery by an endometriotic lesion of the left ovary. DESIGN: Case report and review of literature. SETTING: University medical center. PATIENT(S): A 39-year-old nulliparous woman with stage 3 endometriosis. INTERVENTION(S): Operative laparoscopy followed by laparotomy, oophorectomy, and ligation of the bleeding uterine artery. RESULT(S): Patient is fully recovered and is attempting to conceive. CONCLUSION(S): An endometriotic lesion eroded the wall of the uterine artery, causing massive, acute hemoperitoneum. Such an event may be overlooked during laparotomy and attributed to the trauma of surgery.