The rheological properties (viscosity and principal normal stress difference) of poly-styrene–styrene solutions at concentrations of 15, 20, 30, 35, 43, 50 and 57 wt-% have been measured at 60°C. The flow patterns around a sphere, disc, turbine, and screw propellers in such solutions have also been determined. The second-order fluid theory of viscoelastic fluids containing parameters determined from our rheological measurements has been used to predict the flow patterns about the sphere. The observed flow patterns are in good agreement with the theoretical predictions based upon externally measured rheological properties. The implications of this study of this behavior of batch and CSTR polymerization reactors are discussed.