Based on Biot’s theory for the propagation of sound in a fluid-saturated porous medium, the viscous attenuation of sound has been studied both theoretically and experimentally. It is shown that the important dynamic parameters can be derived from a knowledge of the permeability, grain size, and porosity. Measurements in uniform sized beads show attenuation and velocity dispersion as a function of frequency in agreement with the theory. A comparison between theoretical viscous attenuation and earlier reported measurements indicates that viscous losses may be of significant importance for higher frequencies in sands of high permeability.