The aim of this study is the creation of an empirical model that can be used to predict the viscosity of a semicrystalline polymer melt for polymer process control. We have developed an empirical viscosity equation from both analysis and experimentation that takes into consideration the effect of temperature on both the flow behavior and the consistency index in the power law. The analysis is based on previously published literature, whereas the experimental data have been obtained from both the literature and laboratory investigations. The coefficients of the empirical model for low-density polyethylene and polypropylene have been obtained from the experimental data derived from capillary rheometer measurements in the laboratory. This empirical model is able to produce results matching the experimental data with remarkable accuracy. (C) 2003 Wiley Periodicals, Inc.