The temperature dependence of the dynamic mechanical and a.c. electrical properties of a given polyvinyl chloride plasticizer composition can be characterized by two quantities: (a) the transition temperature which is defined as the temperature of maximum dissipation factor and (b) the half‐widths of the loss factor‐temperature curve. A simple relationship exists between the transition temperature determined mechanically or electrically and the volume fraction of a compatible plasticizer. The modification of this relationship for non‐compatible plasticizer has been indicated. The half‐width is a function of the volume fraction of the plasticizer, although this relationship is not as simple as the one obtained for the transition temperature. A simple correlation exists between the electrical and mechanical half‐width. The compliance measured in tensile creep has been found to be a function of the applied load and the compliance‐load relationship varies depending on the region in which the material finds itself. The shape of the creep curve at different temperatures has been correlated with the dissipation factor‐temperature curve. The shape of the stress‐strain curve has been related to the modulus‐temperature curve and a correlation between the initial Young's modulus and the ultimate elongation and breaking strength has been established. It has been shown that the relaxation theory is not sufficient to explain certain features of the modulus (or dissipation factor) temperature relationship. The limited significance of the &mgr;‐value and of the viscosity of plasticizers with respect to plasticizer efficiency has been demonstrated.