In this paper we review some fundamental issues that have been identified by macroeconomists in discussing the co-ordination of monetary and fiscal policy. As Sargent and Wallace (1981) graphically illustrated, the consolidated public sector present-value budget constraint means that monetary and fiscal policy are ultimately joint decisions. However, as we show in a quantitative general equilibrium model, even when fiscal solvency is not an issue, monetary and fiscal policy may still need to be co-ordinated.