The main goal of this work is to publish the results of an inter-comparison simulation exercise of a clinical 10x10 cm 2 beam model of a 6 MV LINAC using two different Monte Carlo codes: the MCNPX and EGSnrc. Results obtained for the dosimetric parameters PDD20,10 and TPR20,10 were compared with experimental data obtained in Radiotherapy and Megavoltage Institute of Minas Gerais. The main challenges on the computational modeling of this system are reported and discussed for didactic purposes in the area of modeling and simulation.