The recent liberalization of rail freight services in Europe has created the possibility of cross-border competition and market integration for European rail freight operators. In other regulated network industries, such as the electricity sector, liberalization subsequently led to a significant number of cross-border mergers. A merger wave also followed the deregulation of U.S. rail freight in the early 1980s. It is therefore not unlikely that an increased number of rail freight mergers might occur in Europe in the upcoming years. This article discusses the competitive effects of such mergers in the context of recently liberalized markets. In particular, it draws from the experience of recent cross-border mergers that were notified before the European Commission. This article proposes several conclusions for market definition, the assessment of the theory of harm, and possible efficiency defenses.