From November 1, 1987, to July 1, 1988, 506 asymptomatic patients 40 years or older underwent screening vaginal sonography at the University of Kentucky Medical Center. Eligibility requirements included no known pelvic symptoms or clinical abnormalities, no history of pelvic radiation, and no history of ovarian cancer. Each ovary was measured in three planes and ovarian volume was calculated using the prolate ellipsoid formula. Ovarian morphology was classified as uniformly hypoechogenic, cystic, solid, or complex. The upper limit of normal for ovarian volume was 18 cm3 in premenopausal women and 8 cm3 in post-menopausal women. With respect to these criteria, 12 patients (2.4%) were noted to have abnormal sonograms, and 10 agreed to surgery. All 10 patients had ovarian tumors with dimensions equal to those predicted by ultrasound. These tumors included four serous cystadenomas, three endometriomas, two cystic teratomas, and one adenocarcinoma. Vaginal sonography is a relatively simple test that can detect subtle changes in ovarian size and morphology. Further evaluation of this test as a screening method for ovarian cancer should be performed in the setting of controlled clinical trials that emphasize cost control and strict patient follow-up.