The question how mergers affect innovation has gained prominence in a number of recent merger cases. Accounting for the likely effects of mergers on innovation is difficult for a number of reasons though. First of all, the relationship between market concentration and innovation is far from clear and not unambiguous. While it is an empirical regularity and, hence, a useful presumption that an increase in market concentration also leads to an increase in price, the case for a similarly general presumption with respect to mergers and innovation is relatively weak. Secondly, while mergers may result in innovation efficiencies, these may be difficult to demonstrate, given that the European Commission requires the efficiencies to accrue in a timely fashion, i.e., within two to four years after the merger. This contrasts with the timespan applied to the theories of harm which the Commission itself employs. This structural asymmetry tends to bias the framework against innovation efficiencies. Thirdly, remedies are notoriously difficult to design, and this is even more valid for innovation markets. In addition, competitors may choose to strategically not disclose part of their research ideas and pipelines in order to sabotage a competing merger if that merger would be procompetitive. Hence, the market test for remedies, which is already difficult in other merger cases, given market participants' strategic interests, will be even more difficult for innovation markets where competing firms can easily hide their intentions, research ides and pipelines.