The application of ultrasound to animals has had a very close relationship to medical applications, as shown by the first animal evaluation publication in the United States in 1956.1 Back fat thickness was measured on beef cattle at Colorado A & M College, now Colorado State University, with a “somascope” ultrasonic unit previously used by the group led by Douglass Howry, MD, at the University of Colorado Medical Center. Staff members from both institutions were listed as coauthors. At about this same time in Europe, industrial A-mode ultrasonic metal flaw detection equipment was used for measuring back fat thickness in pigs.2,3 At the Department of Animal Science, Cornell University, I recognized that it was important to measure muscle mass, such as rib eye depth or area, in addition to back fat thickness, for improved accuracy in predicting body composition. I first made a series of A-mode measurements at specific intervals and angles in 19594 with the Sperry Reflectoscope (Sperry Company, Danbury, CT) and a 1-MHz transducer shown in Figure 1 and then plotted the values on paper. This procedure provided better results than the single A-mode depth readings, but it was apparent that a multiposition scanning technique was required to eliminate “false” echoes and to produce better images, similar to the developments of Howry and Bliss.5 Because it was not practical to place a live animal in a “water tank,” I developed a continuous mechanical scanning procedure, as illustrated in Figure 2. An electric motor was mounted on a thick rubber belt that was placed on the animal’s back. The motor moved a transducer horizontally as it was held vertically by an operator. The movement of the camera back and film was controlled by a synchronized motor to record the image as the lens was open during the entire 10-second scan. The image on Polaroid film developed in about 1 minute (Figure 3) and was evaluated and subsequently measured. This technology was used to evaluate the fat and muscling of all the steers in the Quality Beef Contest at the International Livestock Exposition (Chicago, IL) in 1960, 1961, and 1962. These predicted carcass measurements were provided to the judges for assistance in the ranking of the live animals. Before this time, the cattle judges used only visual appraisal. There was a great need for objective evaluation because it was acknowledged that it was difficult to estimate visually what was under the hide of an animal.