In this paper, we introduce a sequent calculus CIRC for propositional Circumscription. This work is part of a larger project, aiming at a uniform proof-theoretic reconstruction of the major families of non-monotonic logics. Among the novelties of the calculus, we mention that CIRC is analytic and comprises an axiomatic rejection method, which allows for a fully detailed formalization of the nonmonotonic aspects of inference.