This paper examines the link between fiscal rules and public investment both normatively and empirically. We first review the arguments for and against including public investment spending in a fiscal deficit rule. We then seek to assess the determinants of public investment, with a special focus on the role of the fiscal rules embodied in EMU. We conclude that there are practical difficulties precluding the introduction of a 'golden rule' and that there is virtually no evidence that EMU would have affected public investment. Therefore, the focus on safeguarding the level of public investment is somewhat misplaced; instead, one should focus on safeguarding its productivity.