General 2d dilaton theories, containing spherically symmetric gravity and h
ence the Schwarzschild black hole as a special case, are quantized by an ex
act path integral of their geometric (Cartan) variables. Matter, represente
d by minimally coupled massless scalar fields is treated in terms of a syst
ematic perturbation theory. The crucial prerequisite for our approach is th
e use of a temporal gauge for the spin connection and for light-cone compon
ents of the zweibeins which amounts to an Eddington-Finkelstein gauge for t
he metric. We derive the generating functional in its most general form whi
ch allows a perturbation theory in the scalar fields. The relation of the z
ero order functional to the classical solution is established. As an exampl
e we derive the effective (gravitationally) induced 4-vertex for scalar fie
lds. (C) 1999 Elsevier Science B.V.