Abstract: The goal of this paper is to develop, axiomatically, a revealed preference theory of reference-dependent choice behavior. Instead of taking the "reference" for an agent as exogenously given in the description of a choice problem, we suitably relax the Weak Axiom of Revealed Preference to obtain, endogeneously, the existence of reference alternatives as well as the structure of choice behavior conditional on those alternatives. We also elaborate on how to make welfare evaluations on the basis of the resulting individual decision-making model, and introduce the notion of "cumulative reference."