Echinococcal disease remains a problem within some endemic areas. Echinococcal cysts usually involve the liver and lungs,but any other organ can potentially be involved.Extrahepatic localization is reported in14%-19% of all cases of abdominal hydatid disease. We report the case of a large echinococcal cyst localized in the lower pelvis. A 28-year-old woman was admitted to a surgical ward with lower abdominal pain and discomfort lasting for a month. Ultrasonography and computed tomography scanning revealed a large retroperitoneal cystic mass (9 cm×4 cm) in contact with the left ovary and leftureter. There were no cysts in any other location.Serological tests were positive for Echinococcus. The patient was operated on and the entire cyst was excised intact. Histopathological results confirmed the diagnosis of chinococcosis.ntihelminthics were administered postoperatively and the patient was discharged after 6 d,and is now being closely followed up. Total cystectomy when possible represents the treatment of choice for large extrahepatic echinococcal cysts.