We report a case of huge ovarian cyst, which we met very rarely today, although a good many reports were found in the past literature. A 54-year-old mutiparous housewife was admitted to the Han-Il Hospital on Feb.25, 1980, complaining of the enlargement of the abdomen and inability to walk. Her height was 162 cm, body weight, 70 kg and the abdominal circumference was 130 cm on admission. The tumor was removed surgically after puncture aspiration of cystic contents. It proved that it had originated from left ovary. The tumor weighed 31.04 kg and the colume of cystic contents was 28 L. Pathologi diagnosis was, "mucinou cystadenoma, giant, left ovary". Hospital course ahd been unevenful and the patients was discharged on the postop. 8th day.