AbstractA variety of constitutive equations have been proposed in recent years to describe the behaviour of polymer solutions and melts. Rather complete reviews of most of the differential and integral equations proposed prior to 1967 have been given by Spriggs, Huppler and Bird(1)and by Bogue and Doughty(2,3). Since then, numerous efforts have been directed towards the development of equations capable of predicting adequately nonlinear and transient properties of polymer solutions and melts.Considerable information can be found in the recently published works by Bird et al.(4,5).Some of the more successful models are presented here in an uniform notation. The models are evaluated in terms of their ability to simultaneously describe some or most of the rheological functions such as the non‐Newtonian viscosity, the normal stress difference functions, the components of the complex viscosity, stress growth and stress relaxatio