Simulation de gerbes atmosphériques du aux rayons cosmiques

We present recent developments concerning the simulation of air showers from cosmic rays at the highest energies. Progress is mainly due to new hadronic interaction models, which take into account the wealth of information obtained at the RHIC collider, in addition to the existing data from SPS and Tevatron. Interesting is in particular the fact that considerably more muons are produced compared to older shower simulations.