This article describes an experimental apparatus and analysis scheme for determining the viscoelastic properties of a material isothermally, with a single apparatus, over 10 decades of time and frequency. Torque was applied to the specimen electromagnetically and its deformation was determined by laser interferometry. Resonances were eliminated from the torque and angle measuring devices by this approach. Resonances remaining in the specimen itself were corrected by a numerical analysis scheme based on an analytical solution which is applicable to homogeneous cylindrical specimens of any degree of loss. The apparatus is capable of creep, constant load rate, subresonant dynamic, and resonant dynamic experiments in bending and torsion. The range of equivalent frequency for torsion is from less than10−6 Hzto about104 Hz.The capability of the apparatus is illustrated with measurements upon several viscoelastic elastomers and upon poly(methyl)methacrylate.