Abstract. The main aim of this thesis is the generalization of results about the regularity of CR mappings given by Lamel and Berhanu-Xiao to the ultradifferentiable category. Here ultradifferentiable is understood in the sense of Denjoy-Carleman classes $\mathcal E_{\mathcal M}$, i.e. subalgebras of smooth functions defined by weight sequences $\mathcal{M}$.
To this end a geometric theory of the ultradifferentiable wavefront, $\mathrm{WF}_{\mathcal M}$, that was initially defined by Hörmander,  is developed.
In particular, Bony's Theorem is generalized to the ultradifferentiable setting, which in turn allows to define $\mathrm{WF}_{\mathcal M} u$  for a distribution $u$ defined on a manifold of class $\{\mathcal{M}\}$.
Furthermore an ultradifferentiable microlocal elliptic regularity theorem is shown for vector-valued distributions and partial differential operators with ultradifferentiable coefficients. This fact is also used to give quasianalytic versions of the Holmgren Uniqueness Theorem and generalizations due to Bony, Sjöstrand and Zachmanoglou.
Finally these microlocal techniques can be applied to straightforward generalize the results of Fürdös-Lamel regarding the regularity of infinitesimal CR automorphisms.