In this paper, we determine the complexity of propositional theory curbing. Theory Curbing is a nonmonotonic technique of common sense reasoning that is based on model minimality but unlike circumscription treats disjunction inclusively. In an earlier paper, theory curbing was shown to be feasible in PSPACE, but the precise complexity was left open. In the present paper we prove it to be PSPACE-complete. In particular, we show that both the model checking and the inferencing problem under curbed theories are PSPACE complete. We also study relevant cases where the complexity of theory curbing is located