We have obtained results that show that acoustic absorption in linear polysiloxanes varies with viscosity and frequency in a unique manner. At any constant temperature, a significant relaxation is found, with a broad spectrum of relaxation frequencies. On the other hand, the absorption shows a monotonic rise with increasing viscosity up to very high viscosities. For this reason, there is some doubt as to how to treat the data by means of reduced variables. Shear impedance has recently been measured in the same liquids over a wide range of frequency and viscosity, and dynamic viscosities have been computed. We have also attempted to show that there exists in general a simple relaxation between the acoustic absorption and the dynamic viscosity. It is not clear, however, that the two are uniquely related. [Work sponsored by the Acoustics Branch, U. S. Office of Naval Research.]