An automated dynamic mechanical spectrometer suitable for the testing of low stiffness specimens, e.g. cellular plastics, is described which operates in the frequency range 0.07 to 100 Hz. The mechanical properties of resilient materials are of interest because of their wide application in dynamic situations. The spectrometer uses a novel algorithm to determine the amplitude and phase of the force and displacement signals. The system also allows automatic mass compensation. The essential features of the system are described and measured data are given for conventional test pieces and foams filled with incompressible fluid.