Simulations of the elastic deflection of a 1.2 m slit die under load during the extrusion process have been performed, using the commercial finite element package MARC. The melt pressure distribution needed to assign the loads to the MARC package was previously obtained by a Hele-Shaw based finite element program, and was thus not coupled with the deflection analysis. Existing analytical calculation methods for deflection are also examined. Experiments using production scale machinery have been conducted to record the die deformations under different melt pressures and compared with the computed data. Analytic deflection predictions are shown to be inadequate. The numerical results are fair, but it is clear that coupling of flow and deflection analyses is essential.