We use a very general bivariate GARCH-M model and monthly data on EU countries covering the 1962-2003 period to test for the impact of real (output growth) and nominal (inflation) macroeconomic uncertainty on inflation and output growth. Our evidence supports a number of important conclusions. First, in the majority of countries uncertainty regarding the output growth rate is related to the average growth rate and the effect in several countries is negative. Second, in half of the cases there is no significant relationship between inflation uncertainty and output growth performance. Third, inflation and output uncertainty have a mixed effect on inflation. Nevertheless, considerable evidence for the Cukierman-Meltzer hypothesis is obtained. Our conclusions are based on adopting both a structural and a reduced-form bivariate GARCH model. Finally, we also find statistically significant evidence of regime switching for both inflation and output growth volatility throughout the sample.