Open books for contact five manifolds and applications of contact homology In the first half of this thesis we use Girouxs construction of contact open books to construct contact structures on simply connected five manifolds. This allows us to reprove a theorem of Geiges concerning the existence of contact structures in all homotopy classes of almost contact structures on simply connected five manifolds. In the second part of this thesis we give an algorithm for computing the contact homology of some Brieskorn manifolds. As an application we construct infinitely many contact structures on the class of simply connected contact manifolds that admit nice contact forms (i.e. no Reeb orbits of degree 1 0 or 1) and have index positivity with trivial first Chern class. In particular we give examples of simply connected five manifolds with infinitely many contact structures.