The ultrasonic absorption coefficient has been measured in single benzene crystals along the principal crystallographic axis. The range 6–38 MHz and at temperatures between 170° and 250°K. All three cases indicated a relaxation frequency near the middle of the frequency range (different in each case), and the values along thea‐ andc‐axes suggest the presence of other relaxation frequencies. The measurements have been compared in detail with the theories of Liebermann and Danielmeyer, but the agreement is far from satisfactory.