Of 1757 consecutive women patients examined with ultrasound (US) between 1983-1986, 796 patients were asymptomatic, had no masses on their mammograms, and were scanned with whole breast US because their breasts were radiodense on mammography. Combinations of automated and real-time hand-held equipment, ranging in frequency from 3.9 MHz to 10 MHz. were used. Of the 796 examinations, 71.5%(569) were normal, 23.5%(187) disclosed cysts, and 4.3%(40) revealed solid masses. Four masses were biopsied, yielding one malignancy, two fibroadenomas and one normal breast tissue. All but 4 of the remaining 36 asymptomatic women with solid masses had a follow-up period of at least 1 year. In the authors' opinion, this low yield of one breast cancer in 796 asymptomatic women implies that whole breast US is of little value (in terms of breast cancer detection) in breasts that are radiodense but otherwise negative on mammography.