The main focus of this presentation is to describe the use of a new ultrasonic device, the Scanning Acoustic Microscope (SAM), for grain structural studies. The acoustic microscope, which uses ultrasonic waves which cover a frequency range from 20 MHz to 2 GHz, is a novel ultrasonic imaging technique and produces images comparable to the optical microscope. The significance of the acoustic microscope does not lie in its resolution alone. There are several advantages to using acoustic waves for producing images, e.g. ultrasonic waves penetrate materials that are opaque to optical waves, the distinctive origin of the contrast in the mechanical properties allows one to obtain quantitative information about grain structures, boundary imperfections, etc. Several examples of SAM applications will be presented. Advantages and disadvantages of the contrast mechanism inherent with the scanning acoustic microscope will be discussed.