Experimental measurements of birefringence and velocity gradient components are reported for steady mixed type flows of a0.076 g/cm3solution of2.89×106 MWpolystyrene in a mixed toluene/oligomer solvent. The flow field is produced in a co-rotating two-roll mill with a series of different ratios of the gap width to roller radius chosen so that the flow type at the stagnation point for a Newtonian fluid would range from0.0196⩽λ⩽0.20,where‖E‖/‖Ω‖=(1+λ)/(1−λ).Additional data are also reported, for comparison purposes, for a similar polystyrene solution in a simple Couette flow. Finally, the stress-optical relationship is used to obtain a generalized extensional viscosity as a function of strain rate. This viscosity shows a range of strain rate thinning as predicted by reptation theory, followed at a critical Weissenberg number of 0(1) based on the Rouse relaxation time by the initial stages of a region of strain rate thickening, as predicted by the Marrucci–Grizzuti extension of reptation theory that allows for stretching of the primitive chain. Detailed comparisons with birefringence predictions from this model, using measured flow data as input, show good qualitative agreement but a number of quantitative differences. Most notable are: the fact that the model predicts an orientation angle that is rotated further from the principal strain rate direction than what is observed experimentally, especially for the smallest λ values; the lack of a distinct plateau region prior to the onset of chain stretch; and a rate of increase of steady state chain stretching with Weissenberg number that is significantly weaker in the experiments than what is predicted via the model.