Pressure effect of steady shear viscosity for viscoelastic fluids during die extrusion flow has been analyzed and discussed. On the basis of simplified conditions, an expression for estimating the pressure coefficient (beta) has been proposed in the present article. The sensitivity of melt shear viscosity to pressure during the die extrusion flow of natural rubber (NR)/styrene-butadiene rubber (SBR) blend (a tread rubber), a low-density polyethylene (LDPE) and a polystyrene (PS), has been studied by using a capillary rheometer under testing conditions. The results show that values of beta calculated using this equation based on the measured data from the samples are close to the values reported in literature. In addition, it is shown that beta decreases with increasing extrusion flow rates and a rise in temperatures. (C) 2001 Elsevier Science Ltd. All rights reserved.