The purpose of this study was to evaluate bilateral oophorectomy in women over 50 years old found to have an adnexal mass using transvaginal ultrasonography (TVS) as a mass screening. With TVS a total of 23,451 women without symptoms were examined for ovarian cancer at annual screening for uterine cervical cancer. Two hundred fifty-eight women over 50 years old persistently had abnormal TVS results and 95 women gave informed consent for surgical tumor removal. In the 95 women operated, 7 malignant ovarian cancers were found. Especially adnexal masses which were thought to be benign were treated by laparoscopic surgery.