A 16-year-old girl sought medical attention at the Mayo Clinic because of a 4.5-kg weight loss, hypercalcemia, and a pelvic mass. Preoperatively, the level of the beta-subunit of human chorionic gonadotropin was 147 IU/liter. After a brief period for observation and hydration, abdominal exploration revealed a stage III dysgerminoma; total abdominal hysterectomy and bilateral salpingo-oophorectomy were performed. Within the dysgerminoma, syncytial giant cells expressed human chorionic gonadotropin-positive immunostaining in the cytoplasm. Postoperatively, the value of the beta-subunit of human chorionic gonadotropin decreased rapidly. The patient received whole-abdomen irradiation 4 weeks postoperatively, after which the level of calcium returned to normal. The patient has been free of disease for more than 7 years.