This paper reviews the literature on Ricardian equivalence. This hypothesis may be interpreted as a generalization to the short and the long run of the theories that put no weight on the real effects of public policies on aggregate demand. We argue that Ricardian equivalence relies on both the permanent income hypothesis and the fulfillment of the intertemporal government budget constraint. The theoretical literature emphasizes several reasons for departures from this hypothesis. However, the empirical literature is inconclusive. When Ricardian equivalence is tested in a life–cycle framework the hypothesis is usually rejected, while when the empirical analysis is based on optimizing models, it is usually accepted.