Rheogoniometric and fiber spinning experiments were carried out using polyacrylamide solutions containing 100, 200, and 300 ppm of polymer. The stress levels in the extensional flow experiments were 1–3 orders of magnitude greater than those which would have been exhibited by Newtonian fluids of identical viscosity level. Since the stresses arising in extensional flows of simple fluids are very sensitive to the distant deformation history of the material,whereas the recent history is of dominant importance in shearing flows, the ability to model both deformation processes with a common constitutive equation is a very severe test of the latter, and one which is of importance in a variety of processing areas. An evaluation of several constitutive relations is presented; two derivative models are found to portray the results with reasonable accuracy, although a given set of material parameters does not suffice for predicting all of the stresses measured in both shearing and extension.