Vicious, i.e. non-intersecting, random walkers have been studied in various physical situations, ranging from wetting and melting to stochastic growth processes.  In this talk, I will present a method based on path integrals associated to free Fermions models to study such statistical models.  In particular I will show how this allows for a physical derivation of the connection between certain constrained vicious walkers and random matrix theory.  Besides I will use this method to calculate exactly the distribution of the maximal height of p vicious walkers with and without a wall.