The energy dissipation in a single degree of freedom linear vibration damper, consisting of a mass suspended on a 'spring' made from viscoelastic material, was investigated both analytically and experimentally. Analytical techniques utilizing measured values of the complex modulus of a few ''typical'' viscoelastic materials are described. The effects of changes of material properties with temperature and frequency are considered. It is shown that a damper of this type is effective at frequencies near its undamped resonant frequency and above. A unique experimental technique for measuring the energy dissipated per cycle in the damper is described. Phase and amplitude calibrations, together with the method used for mass cancellation, are discussed. Agreement between analysis and experiment is shown to be generally within the accuracy of most of the complex modulus data currently available for damping materials.