We prospectively assessed the accuracy of high resolution breast ultrasonography in the diagnosis of palpable breast masses in comparison to clinical palpation and x-ray mammography. Four hundred and eight Chinese women with palpable breast lumps had clinical assessment followed by ultrasonography of the breast, mammography (for women over 35 years), and fine needle aspiration cytology. Excisional biopsy or surgery was performed for suggestive lesions. The clinical, mammographic and ultrasound diagnoses were compared with the final pathologic diagnosis. In the determination of whether a lesion was malignant, the sensitivity, specificity, and positive predictive values were 97%, 97%, and 85%, respectively, for ultrasonography; 92%, 94%, and 84%, respectively, for mammography; and 88%, 92%, and 67%, respectively, for clinical evaluation. The specificity for combined clinical palpation and ultrasonography was higher (99%) than that for combined clinical palpation and mammography (96%). Addition of ultrasonography to combined clinical palpation and mammography increased specificity. Mammography in addition to combined clinical palpation and ultrasonography did not significantly improve the sensitivity, specificity, or positive predictive value. This limited usefulness raises the question as to whether it should be eliminated in the workup of a palpable mass in the average Chinese patient. Its main advantage is the detection of extended foci of carcinoma in situ related to a palpable mass, which often is undetected by ultrasonography.