Recommended surveillance for screening breast cancer, which includes regular mammography and clinical breast examination, has long been established in Western countries. This strategy may be too costly and unnecessary for countries with low incidences of breast cancer. The purpose of the present study is to compare breast mammography, sonography and physical examination in screening female relatives of breast cancer index cases from the hospital, and their relative efficiency. A total of 935 women over 35 years old, who were relatives of breast cancer patients, were invited to an annual screening by means of a combination of mammography, sonography and physical examination on a single day. A biopsy was performed when any of the three investigations indicated a possibility of malignancy. A total of 21 breast cancers, including sixteen invasive cancers and 5 noninvasive cancers, were detected among the 935 high-risk women. Of the cancers, 18, including 16 invasive cancers and 3 noninvasive cancers, were detected by sonography. In contrast, only 11 invasive cancers were detected by mammography, and 7 by physical examination. There were only 14 cancers detected by a combination of mammography and physical examination. The 7 (33.3%) additional cancers were detected when sonography was added. The sensitivity of sonography was 90.4%, which was higher than mammography (52.4%) and physical examination (33.3%), or even a combination of these two modalities (66.7%). This indicates that sonography is a more accurate screening tool for breast cancer in the high-risk group. Although breast sonography has not yet been recommended as a routine screening tool for breast cancer in Western countries, it may be superior to mammography and physical examination for the screening of Taiwanese high-risk female relatives of breast cancer index cases. If it should also be considered as a routine adjunct screening modality for Taiwanese women with lower rates of breast cancer will need further study.