Of the total subjects, 588 women (72.5%) were symptomatic when they underwent breast US. A palpable mass was the most common reason for referral (n=451). The most common reason for referral for asymptomatic women was routine screening (n=111). US findings were classified as category 1 (n=192), category 2 (n=81), category 3 (n=399), category 4 (n=134), and category 5 (n=5). The PPVs for category 1, 2, 3, 4, and 5 were 0, 0, 0.3, 6.3, and 100% in the symptomatic group, respectively. For the asymptomatic group, the PPVs were 0, 0, 0, 8.7, and 100%, respectively. More cancers were found in high risk women (22.2%, 4/18) than in non-high risk women (1.4%, 11/793).