Cosmological solutions of the Einstein Vlasov scalar field system The aim of this thesis is to obtain as much information as possible about global solutions of the Cauchy problem for the Einstein Vlasov scalar field system with spherical plane and hyberbolic symmetries written in areal coordinates. The sources of this system are generated by both a distribution function and a linear scalar field subject to the Vlasov and wave equations respectively. This system describes the evolution of self gravitating collisionless matter and scalar waves within the context of general relativity. We consider the cosmological case. That is spacetimes possess a compact Cauchy hypersurface and then data are given on a compact 3 manifold. We extend the local in time results obtained by G. Rein for the Einstein Vlasov system with collisionless matter alone. This extension concerns pointwise estimates for hyperbolic equations by the method of characteristics. This means that the system is transformed to a system of ordinary differential equations which are integrated along characteristics ...