Describes a forced, nonresonance method for determining the components of the tensile complex modulus of polymers at frequencies typically in the range 0,01 Hz to 100 Hz. The method is suitable for measuring dynamic storage moduli in the range 0,01 GPa to 5 GPa and to the measurement of loss factors greater than 0,1 und may therefore be conveniently used to study the variation of dynamic properties with temperature and frequency through most of the glass-rubber relaxation region.