The paper presents medium-term fiscal challenges faced by the Republic of Slovenia upon its accession to the European Union. At the beginning, two methodological issues are discussed. First, the difference between the calculated and actual net transfers between the EU budget and national budgets of the EU member states. Second, typology of fiscal effects the EU funds have on a member state's national budget, both on its overall level and on its expenditure structure. The following two parts of the paper provide quantification and an analysis of effects the EU membership is expected to have on Slovenia's public finances in early post-EU accession years, i.e. in the 2004 - 2006 period, and in the period of the next medium-term financial perspective of the EU, covering the period between the years 2007 and 2013.