Dynamic mechanical properties of EPDM gum vulcanizates were studied using the dynamic viscoelastometer, Rheovibron. A small sinusoidal strain was superimposed on a static strain and its effect on dynamic mechanical properties were analyzed. The results are discussed in terms of total strain which takes the static strain into account. Separability of time and strain effects for loss modulus and the nonseparability for storage modulus are discussed. A critical strain was identified after which the stress dissipation mechanism changes.