The complete characterization of tissue is extremely important for objectively identifying abnormalities and disease states. Optical methods of microscopy have been exploited to a great degree and now the electron microscope is being used in search of diagnostic clues at higher magnification levels. It is well appreciated, however, that these methods provide only limited access to the physical properties of tissue. Furthermore, the physical nature of an abnormality may prohibit its ever being revealed with visual observation techniques. Acoustic microscopy, on the other hand, can reveal new information, the structural elastic characteristics of viable tissue. Acoustic microscopy can also provide quantitative data on these tissue characteristics. As this additional information should have great diagnostic value, a general discussion of the methods and procedures employed is presented.