Merger control constitutes a well-established pillar of EU competition law. However, the drafters of the Community competition merger legislation, in view of the need to attain the imperative goal of market integration, put more emphasis on the clarification of the substantive rules applied by the Commission through enhancing its supervisory powers than on the necessity for protecting the defendant parties or any involved third parties in merger proceedings. Here for the first time is an in-depth analysis of the rights of notifying parties and third parties in merger proceedings, as reflected in the administrative practice of the Commission and the case law of the Community courts. Following a detailed exposition of the operation of the Merger Regulation and its procedures, this study covers not only the generally approved fundamental rights, such as the right to be heard or the right to access the Commission s file, but also all the other procedural rights involved in merger proceedings, such as the right of notifying parties to propose commitments outside the time-limit required. It examines the rights of the parties from the pre-notification stage through the first and second phases of the proceedings, with particular emphasis on notification, preliminary investigation, statement of objections, access to the file, oral hearing, commitments, and adoption of the final decision.