  For a compact Riemannian manifold, Weyl's law describes the asymptotic
behavior of the counting function of the eigenvalues of the associated Laplace
operator. In this paper we discuss Weyl's law in the context of automorphic
forms. The underlying manifolds are locally symmetric spaces of finite volume.
In the non-compact case Weyl's law is closely related to the problem of
existence of cusp forms.
