The aim of this paper is to contribute to the research on the relationship between banking efficiency and European financial integration. It estimates cost translog frontier functions for two panels of European Union countries—one that includes all 27 member states and another composed of the 15 “old” members only—just before the recent crisis. The main conclusions point to the persistence of technical bank cost inefficiency during a relatively long time period, 1994–2008, and in spite of the decrease of the country inefficiencies between 2000 and 2008, there are no remarkable changes in the countries' ranking positions. Additionally, there is evidence of quite a slow convergence process across European Union bank sector performance, a process that accelerates slightly after 2000