Background: Ovarian choriocarcinoma(CC) is rarely encountered as compared to uterine CC. Furthermore, ovarian CC coexisting with surface epithelial tumor is very rare. Case: A 50-year-old postmenopausal woman, gravida 0, was admitted to our hospital with abdominal pain and distention due to a complex ovarian tumor. The laboratory data showed high serum level of CA125, neuron specific enolase(NSE), and hCG β-subunit C-terminal peptide(hCG-β-CTP). Total abdominal hysterectomy, right salpingoophorectomy, and lymph node dissection were performed. The right ovary revealed a cystic tumor with two solid parts: larger part, endometrioid adenocarcinoma and small cell carcinoma; smaller part, predominantly CC and focally clear cell adenocarcinoma. CA125 was rapidly decreased after first operation, but hCG-β-CTP levels repeated distinctive fluctuations and NSE abruptly increased during the last few months before death. The patient died 10 months after the first operation. Conclusion: Only four cases of ovarian nongestational CC coexisting with surface epithelial tumor have been reported. This is the first reported case of admixture of CC with three epithelial malignancies. We assume that endometrioid and clear cell adenocarcinomas arose at different sites as tumorigenic factors in association with endometriosis, and the former may have been dedifferentiated into small cell carcinoma and the latter to CC. Coexistence of CC with small cell carcinoma is considered to be responsible for relative chemoresistance leading to poor prognosis. Background: Ovarian choriocarcinoma (CC) is less encountered as compared to uterine CC. It is very in case of ovarian CC coexisting with surface epithelial tumor is very rare. Case: A 50-year-old postmenopausal woman, gravida 0, was admitted to our hospital with abdominal pain and distention due to a complex ovarian tumor. The laboratory data showed high serum level of CA125, neuron specific enolase (NSE), and hCG β-subunit C-terminal peptide (hCG-β-CTP). Total abdominal hysterectomy, right salpingoophorectomy , and lymph node dissection were performed. The right ovary revealed a cystic tumor with two solid parts: larger part, endometrioid adenocarcinoma and small cell carcinoma; smaller part, predominantly CC and focally clear cell adenocarcinoma. CA125 was rapidly decreased after first operation, but hCG-β-CTP levels repeated distinctive fluctuations and NSE abruptly increased during the last few months before death. The patient died 10 months after the first operation. Conclusion: Only four cases of ovarian nongestational CC coexisting with surface epithelial tumor have been reported. This is the first reported case of admixture of CC with three epithelial malignancies. We assume that endometrioid and clear cell adenocarcinomas arose at different sites as tumorigenic factors in association with endometriosis, and the former may have been dedifferentiated into small cell carcinoma and the latter to CC. Coexistence of CC with small cell carcinoma was considered to be responsible for relative chemoresistance leading to poor prognosis.