In this paper, I analyse the synchronization of business cycles within the E.U., as this is an important ingredient for the implementation of a successful monetary policy. The business cycles of twelve E.U. countries and two sub-groups of countries are extracted for the period 1989Q1-2010Q2. The cycle of G3, the group of the three largest European economies (Germany, France and Italy) is then used as a benchmark series for the comparisons. The sensitivity of the data to alternative cycle extraction methodologies is explored employing the Hodrick-Prescott and Baxter-King filters using alternative parameter specifications and leads/lags. The strength of cycle synchronization is measured using linear regressions, cross-correlation coefficients and the Cycle Synchronization Index (CSI). To assess whether synchronization is stronger after the introduction of the common currency, we also test two sub-samples pre- and post-EMU (1999Q1). The empirical results provide evidence that cycle synchronization within the Eurozone has become stronger in the common currency period.