A three-dimensional numerical model was developed to investigate the nonisothermal, non-Newtonian polymer flow through a cone cylindrical die used in the HDPE (high-density polyethylene) extrusion process. The numerical model was based on the computational fluid dynamics code COMSOL 3.4 the finite element method, and it was used to calculate pressure, flow, and temperature distributions in a cone cylindrical die used for industrial-scale extrusion of an HDPE rod. The model also accounted for viscous heating. In addition, pressure and temperature data were derived using an analytical solution. The numerical approach agrees fairly well with the experimental data recorded during the extrusion process of the material. C (C) 2010 Wiley Periodicals, Inc. Adv Polym Techn 29: 173-184, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20185