In this paper, we review the recent empirical evidence and theoreticallitterature dealing with the relationship between national saving and national investment. We attempt to understand the implications of a deeper economic and monetary integration for a country like Spain. We reach theree main conclusions. First, the increasing degree of capital mobility experienced by Spain will not alterthe basic relationship between national saving and investment. Second, the implementation of fiscal rules similar to those of the Maastricht Treaty may haave important effects and contribute to the weakening of the link between national saving and investment. Finally, such a relationship will become looser if the process of economic and monetary union integration in Europe goes further.