A simple mathematical model is developed to describe a lost foam casting process. Different aspects of the process, such as liquid metal flow, transient heat transfer, foam degradation and gas elimination were incorporated into this numerical model. Fluid velocity, temperature distribution within molten metal and pressure building-up in the mold cavity are predicted as a function of filling time and filling height. The model was verified by comparison of the predicted velocity profiles, temperature fields and back-pressures with the experimental data conducted in this work. Both coated and uncoated foam patterns were used in experimental part of this study. A good agreement between the predictions and the experimental data was found.