Molecular dynamics fails for long time phenomena. At the opposite, pure statistical methods (transition state or RRKM theories) get rid of this problem by phase space volume estimate, but assuming the questionable hypothesis of a fast intra dynamics. We have implemented a mixed statistical dynamical treatment which includes intra dynamics by means of kinetic equations for the states populations. This formalism can be applied either to chemical reactions or to physical chemical processes, such as evaporation or diffusion by jumps.