Pressure distributions along the die axis in a round tube extrusion for a commercial grade polystyrene and a low pressure polyethylene were carried out by using a modified commercial extruder and electric menbrane type pressure gauges. Measured pressure drops along the length of the tube containing a larger preceding channel in diameter were discussed numerically in terms of the tube length correction term coefficient and the viscosity resistance of the flowing liquid. The residual pressure at the tube exit, expected to show the pressure energy necessary to cause the Barus effect, was apparently observed with a tendency to increase with shear rate. Operations of the elastic shear stress in the steady laminar flow were persisted.