Dynamic viscoelastic measurements and extrusion rheometry results of immiscible and partially miscible PVC/EVA blends from 50 to 90 wt% in PVC are presented and compared with those of plasticized PVCs, From loss modulus data the plateau modulus, G(N)(o), associated with entanglements, is calculated. The variation of G(N)(o) will composition is analyzed using the theory of Tsenoglou. A simple model, which accounts for the effect of a structural parameter and the effect of free volume, is used to adjust viscosity data, taken at several frequencies and shear rates. For both types of blends, best its are obtained using a model that establishes that the free volume of each polymer is not measurably altered by the other.