An experimental investigation of the temperature increase due to viscous dissipation in an oscillating pipe flow is presented. An oscillating pipe of circular section, acting as an extrusion die, was placed at the last stage of a polymer extrusion process and the increase in the temperature of the fluid, due to the superimposed oscillation, was measured. Thermocouples and a temperature control system were mounted on the walls of the oscillating section. Experimental results were obtained following the conditions suggested by Casulli et al. [J. Polym. Eng. Sci. 30 (1990) 155 1]. Commercially available low density polyethylene was chosen as the experimental fluid. Results were obtained for the case when the imposed oscillatory motion was parallel to the axial direction of the flow. The bulk temperature of the fluid at the exit of the oscillating section was found to increase with the oscillating frequency and amplitude. If the dimensionless temperature increase is plotted as a function of the characteristic oscillation speed, the experimental results collapse into a single curve. In order to justify the experimental measurements, a theoretical analysis was performed for two simple non-Newtonian fluid models: linear viscoelastic and power-law liquids. Analytic expressions for the velocity and temperature fields were obtained. These models predicted an increase of the bulk temperature with the speed of oscillation in agreement with the experimental results. The direct comparison of the measurements and the predictions showed good order-of-magnitude agreement. We found that the temperature increase predicted using a linear viscoelastic model agrees well with the experiments for low oscillation speeds. For the case of large oscillation speeds, the prediction based on a power-law model resulted in a better agreement than the viscoelastic model prediction.