  In the present note a functional calculus $\phi \mapsto \phi(A)$ for
self-adjoint definitizable linear relation on Krein spaces is developed. This
functional calculus is the proper analogue of $\phi \mapsto \int \phi \, dE$ in
the Hilbert space situation. It also comprises the Spectral Theorem for
self-adjoint definitizable operators on Krein spaces showing the existence of
spectral projections.
