This paper applies a novel methodology to a unique dataset of large concentrations during the period 1990-2002 to assess merger control’s effectiveness. By using data gathered from several sources and employing different evaluation techniques, we analyze the economic effects of the European Commission’s (EC) merger control decisions and distinguish between blockings, clearances with commitments (either behavioral or structural), and outright clearances. We run an event study on merging and rival firms’ stocks to quantify the profitability effects of mergers and merger control decisions. We back up our results and methodology by using alternative measures for the merger’s profitability effects based on balance sheet data and obtain consisten...