In this work an amorphous PS was injection molded into a simple line-gated rectangular cavity. The effect on post-filling pressure curves and temperatures (at the polymer-mold interface) of different holding pressures and times, and of two gate thickness configurations, was analyzed. Molding tests were simulated leading to a good description of pressure evolution in different positions along the flow path for all molding conditions analyzed. Comparison between simulation results and experimental data shows that: considering a rigid mold can lead to predicted values of post-filling pressure profiles much different from experimental ones; heat transfer coefficient description plays a minor role in the prediction of pressure evolution, but its effect is relevant on temperature evolution in layers close to the mold surface.