Benign, mucinous cystadenomas account for 15 per cent of all ovarian neoplasms. Of these, the giant variant occurs rarely. A morbidly obese, 52-year-old, white woman was seen for acute abdominal pain and diagnosed using computerized tomography as having a giant, benign, mucinous cystadenoma. At laparotomy, 21-kg cystic mass attached to the right ovary was removed. Total abdominal hysterectomy and bilateral salpingo-oophorectomy were performed. In such patients, special consideration must be given to hemodynamic and ventilatory monitoring and intraoperative fluid management. Recognition and subsequent surgical management of this and other large abdominal masses can be optimized by thoughtful, preoperative evaluation and careful planning of the operative approach.