Ultrasonic visualization techniques offer many advantages in regard to the detection of both benign and malignant pathologies of the soft tissue re- gions of the human body. In the past 5 years, there has been a remarkable pro- liferation of commercially available ultrasound instrumentation with the consequence that the medical profession has become increasingly aware of the diagnostic advantages, for detection of cancer, of examination by high-frequency sound waves. Yet, despite the fact that the potential of ultrasound as a diagnostic tool for breast cancer detection was demonstrated in the United States over 20 years ago and, further, despite the high in- cidence of breast cancer in the western world, commercial instrumentation specifically designed for ultrasound scanning of the breast did not evolve in the western world during this same period. The result of this lack of standard clinical instrumentation was that the extensive clinical groundwork normally carried out by large numbers of clinicians in the early stages of applying a new diagnostic tool simply did not occur in the western world for ultrasonic examination of the breast. As indicated by Dr. Toshiji Kobayashi's tables of data in this publica- tion, individual research scientists and physicians in many parts of the world, and in particular in Japan, carried out breast visualization studies with a multiplicity of types of ultrasonic instrumentation.