In this study, the experiment of the extrusion lamination process using high-pressure process low-density polyethylene (LDPE) was performed. The nonisothermal viscoelastic simulation of the extrusion lamination experiment was also carried out. The simulation results were in good agreement with the experimental data within wide range of take up velocity and air gap length. We developed the theoretical model based on force balance and deformation type of a film to predict the neck-in behavior in the extrusion lamination or cast film process. It was suggested from the neck-in model that the neck-in correlates with the ratio of planar to uniaxial elongational viscosity. It was confirmed that the neck-in model could predict the film edge shape and neck-in properly for conventional LDPE. POLYM. ENG. SCI., 50:22-31, 2010. (C) 2009 Society of Plastics Engineers