Abdominal pregnancy is extremely rare, but even more unusual is the prolonged retention of an advanced abdominal pregnancy with lithopedion formation. The presentation of lithopedion as an ovarian tumor without a symptom has not been reported in Korea. A 63-yr-old, gravida 2, para 1, woman was referred to us with an abdominal mass. Pelvic examination revealed normal postmenopausal uterus and a fetal head-sized movable hard mass in the lower abdomen. The computed tomographic scan showed a densely echogenic mass of 10-cm in diameter as an ovarian neoplasm. Laparotomy disclosed a lithopedion, of which the bones and cartilages were well preserved. There have been controversies on the treatment of lithopedion. Although some cases are stable for a long time, the morbidity increases when the operation is performed in an elderly patient. So we believe that the surgical intervention should be done as soon as possible after thorough consideration of the morbidity and the risk.