A comparison is made of flow curves for the extrusion of a LLDPE melt through clean metal capillaries and when overcoated by fluoropolymer (FE) process aids. Characteristic differences between the flow traces include a shear-rate dependent reduction in flow resistance due to the presence of FE at the die surface. The FE preferentially wets high energy die surfaces, but interacts very weakly with LLDPE melts, thus acting as a lubricant at the polymer/stationary phase interface, and promoting the slip of LLDPE melts. Arguments are presented showing that the percent slippage time must attain an equilibrium value at high extrusion rates. Flow curves for extrusion through FE-coated dies are divided into distinct regions and the slopes of these have been rationalized by equations that combined the concepts of molecular dynamics and of adhesive failure at the die wall/polymer interface as the origins of slip-stick flow.