Using a sample of 96 mergers notified to the European Commission and logit regression techniques, we analyse the Commission's decision process. We find that the probability of a phase-2 investigation and of a prohibition of the merger increases with the parties' market shares. The probabilities increase also when the Commission finds high entry barriers or that the post-merger market structure is conducive to collusion. We do not find significant effects of bpoliticalQ variables, such as the nationality of the merging firms. D