Resin transfer moulding is a production method of fibre reinforced plastics which involves the flow of a resin through a mould packed with dry reinforcement. As simulation by finite element code can be a useful tool in designing the mould or optimising the process, mathematical modelling of RTM is indispensable. The equations concerning the isothermal RTM process with a Newtonian fluid are implemented in the finite element program VIp, applying the 'thin film approximation'. To validate the code, model experiments are performed in which the position of the front as a function of time is monitored and compared to the results of a finite element simulation. A good agreement between simulation and experiment was found. For further validation of more complex mould geometries a plate with inserts is considered. Again good agreement was found between simulation and experiment was found. The finite element code of VIp proves to give reliable and accurate results in the simulation of the isothermal filling process of RTM and can therefore be used for designing mould geometries or optimisation of the RTM process as a whole.