Since April, 1989 in Aomori Prefecture, mass-screening for ovarian cancer by means of transvaginal ultrasonography has been performed in a mass-screening car at the same time mass-screening for uterine cervical cancer. Subjects for this screening were self referred asymptomatic women 30 years of age or older. Real time ultrasonography was performed with a 5-MHz endovaginal transducer 5 sections for scanning were established by means of a transvaginal probe and all ultrasonic pictures obtained were recorded with an 8mm VTR. For women with abnormal ultrasonic findings, such as an ovary (tumor) over 30mm in size and massive ascites, a second screening or accurate examination was performed by retransvaginal ultrasonography, CT-scan, MRI and a combination assay of tumor markers. The results were as follows: The time required for the first screening, including bimanual examination, collection of Pap smear and ultrasonic examination, was about 60-70 seconds. The total number of screened women was 15,282, and 838 (5.5%) of them needed to receive the follow-up examinations. Laparotomy has been done for 48 women to date and 2 women were found to have premalignant and malignant ovarian tumors.