The paper analyses the first decade of merger control policies both in the European Union and in Italy. The foundations of these policies are considered, and the cases of prohibition and approval with commitments are mainly examined. The analysis clearly shows the high degree of discretionary power owned both by the European Commission and the Italian Authority in evaluating the compatibility of mergers with the competition regulations. This discretionary power allows a quite permissive and flexible attitude towards mergers: in both cases the number of operations prohibited or approved with commitments is particularly small. On the one hand this could indicate that firms generally take into account the limits provided by the regulations in formulating their merger strategies. On the other hand, the control policy, in preventing the anti-competitive effects of mergers, has not to depress the potential pro-efficiency and pro-competitiveness effects. In both EU and Italy, the decisions about cases where mergers were going to significantly enlarge the market shares of leading firms suggest that the control institutions often temperate, at least implicitly, the objectives of market control with objectives of stimulating the competitiveness of the production system.