Existing rheological equations for the rubbery state and for the glassy state are not compatible with each other, in that in the former one assumes incompressible, viscoelastic behavior (the various constitutive equations), whereas in the latter one usually presumes compressible, elastic behavior (linear elasticity theory). While it is true that nonequilibrium volume effects in the glassy state have been dealt with extensively with differential rate theories (notably those of Kovacs), these are not stated in a way which allows combination with existing viscoelastic equations, i.e., those for anisotropic deformations. We present a generalized phenomenological model which brings together these various cases in a single formulation. This allows us, at least in principle, to deal with “coupled effects,” in which volume changes induce anisotropic stresses, or vice versa; such effects occur in practically all polymer processes, in the sense that cooling causes volume changes, but with constraints from the geometry.