BRS symmetry of supergravity in superspace and its projection to component formalism

The BRS symmetry of supergravity theories is geometrically constructed in superspace. The construction is formally identical to the one which holds for gauge theories coupled to gravity. If the classical superspace constraints associated to a given set of auxiliary fields are known it is possible to obtain by projection the whole set of BRS transformation laws in component formalism. We illustrate the method with various representations of N=1, D=4 Poincare supergravity. In particular we consider couplings of Chern-Simons forms. Our analysis proves the absence of U(1) anomaly in the new minimal supergravity for any coupling of matter fields. (orig.)