Data on the tensile yield behavior of poly(vinyl chloride) (PVC), reported in the literature, are interpreted in terms of a model involving a cooperative movement of several independent structural units, all with the same activation enthalpy. This analysis leads to physical parameters such as the internal stress, activation volume, and enthalpy, etc. These values are discussed and compared with those determined from thermodynamical considerations using stress relaxation tests and tensile curves at a constant strain rate.