This part of IS0 6721 describes a forced, nonresonance method for determining the components of the shear complex modulus G* of polymers at frequencies typically in the range 0,Ol Hz to 100 Hz. The method is suitable for measuring dynamic storage moduli in the range 0,l MPa to 50 MPa. Although materials with moduli greater than 50 MPa may be studied, more accurate measurements of their dynamic shear properties can be made using a torsional mode of deformation (see parts 2 and 7 of IS0 6721). This method is particularly suited to the measurement of loss factors greater than 0,l and may therefore be conveniently used to study the variation of dynamic properties with temperature and frequency through most of the glass-rubber relaxation region (see IS0 6721-1:1994, subclause 9.4). The availability of data determined over wide ranges of both frequency and temperature enables master plots to be derived, using frequency/temperature shift procedures, which display dynamic properties over an extended frequency range at different temperatures.