Forty-four pathologically proved mammary carcinomas were studied by clinical examination, xeroradiography, and ultrasonography with a dedicated whole-breast scanner. Abnormalities reflecting carcinoma were shown by echography in 90% of cases and xeromammography in 97%. Ultrasonic manifestations of malignancy were separated into four categories: (a) a solid, hypoechoic mass; (b) a hyperechoic focus; (c) an irregular, echogenic zone of parenchymal disruption; and (d) an atypical cystic mass. Dedicated ultrasound instruments enhance interpretation and improve differential diagnostic capability. Sonography demonstrates abnormalities better and permits superior definition of abnormal characteristics in a dysplastic breast than in a fatty, atrophic breast, while xeromammography may be more reliable in postmenopausal women with fatty breasts than in women with mammographically dense breasts. One limitation of current ultrasound equipment is the inability to consistently demonstrate microcalcification.