Background: Breast ultrasound is the major imaging modality in young women because it incurs no radiation exposure and dense breast tissue, which is common in young women, yields a high rate of false-negative results on mammography. Purpose: To investigate the cancer rates of the sonographic BI-RADS categorization and histopathologic results according to the presence of symptoms in young Asian women. Material and Methods: We included 811 young women under 30 years of age who underwent a breast ultrasound during the study period. The mean age of all subjects was 24.5 years (range 11-29 years). Histopathologic results were compared with the results after application of the BI-RADS categorization. Results: Sonographic 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 cancer rates 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 cancer rates 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). Conclusion: BI-RADS categorization was helpful for predicting the probability of malignancy in young Asian women.