The book discusses the EU competition law regime and practice in respect of cartels and other horizontal agreements between competitors. The part on cartels deals with all aspects of a cartel procedure: what agreements and concerted practices form a cartel; how cartels are detected and how they must be proven; what the investigative powers of the European Commission are in respect of cartels, as well as the different stages of an EU cartel procedure; and how the European Commission sanctions cartels and how its decisions are reviewed by the EU Courts. Finally, the rights of cartel victims are discussed, with an emphasis on the EU legislative developments on private enforcement. The novelty of the book is that each of these topics is discussed both from the perspective of a private practitioner and that of a public enforcer. The private practitioners give an overview of the law as it stands and share their practical experience. Each private practitioner is supplemented by a public enforcer, who approaches the same topic but based on the enforcer's experience with handling cartel cases. The part on other horizontal agreements between competitors gives a framework for the competition law analysis of R&D and specialization agreements, including the applicable block exemption regulations, and for the self-assessment of joint purchasing, joint commercialization and standardization agreements. It concludes with a review of the EU competition rules as they apply to information exchanges between competitors.