From December 1987 to December 1993, 6470 women underwent screening with transvaginal sonography (TVS) as part of the University of Kentucky Ovarian Cancer Screening Project. Two groups of women were eligible to participate in this investigation: (i) asymptomatic postmenopausal patients or patients >50 years of age, and (ii) asymptomatic women >30 years of age with a family history of ovarian cancer. Ovarian volume was calculated using the prolate ellipsoid formula (length x height x width x 0.523). An abnormal sonogram was defined by (1) an ovarian volume >10 cm3 in postmenopausal women or >20 cm3 in premenopausal women, and (2) a papillary or complex tissue projection into a cystic ovarian tumor. All women with an abnormal TVS had a repeat sonogram in 4-6 weeks. Patients with persistently abnormal scans had a serum CA-125 determination, tumor morphology indexing, and color Doppler sonography. Ninety patients (1.4%) with a persisting abnormality on TVS underwent exploratory laparotomy or laparoscopy for tumor removal. Thirty-seven patients had serous cystadenomas and six had primary ovarian cancers. Five patients had Stage IA ovarian cancer and one patient had Stage IIIB disease. Only one of the ovarian cancer patients had a palpable abnormality on pelvic examination, and none had an elevated (>35 u/ml) serum CA-125. All these patients are presently alive and well 1-5 years after conventional therapy. There was one false negative in this study, a 38-year-old white female who was noted to have a small ovarian cancer at the time of laparoscopic prophylactic oophorectomy 11 months after a normal scan. Over 17,000 screening years have been accrued and there have been no deaths from primary ovarian cancer in the screened population. A cost analysis of TVS screening is presented.