Polyurethane Foams are produced by mixing Polyol, Isocyanate and Water. Two chemical reactions are then in competition: isocyanate and water produce CO2 which governs the development of bubbles. The crosslinking reaction between isocyanate and polyol produces the solidification of the polyurethane skeleton. The quality of the foam (bubble size and density) depends on the coupling between these two reactions. If the crosslinking reaction starts too early, the viscosity of the skeleton increases and blocks the foam expansion. On the other hand, if the crosslinking reaction starts too late, the foam collapses because the structure of the skeleton is not strong enough. In order to master the foaming process in a mold of complex geometry it is necessary to identify numerous parameters of the foaming and curing reactions which are coupled with the mass, temperature and momentum balance equations. It is difficult to measure the chemical kinetics parameters as well as the viscosity of the polyol-isocyanate-water mixture because the time scales of CO2 production and polyurethane crosslinking are very short and hardly compatible with the installation of the sample in a Differential Scanning Calorimeter (DSC) and in a parallel plates rheometer. Therefore, the Foamat system (Format Messtechnik GmbH) seems the only suitable system which gives sufficient data to build an efficient lodel. This system consists in a cylindrical reservoir equipped with thermocouple and pressure transducer. The mixture is introduced in the reservoir and the foaming dynamics (the height of the sample as a function of time) is measured simultaneously with the temperature and the pressure development. An analytical model of the foam expansion in the Foamat system is proposed which allow determining the thermodynamic and rheology parameters. A numerical model of foam expansion using REM3D is developed. It allows checking the validity of the hypotheses of the analytical model.