Europe has a long history of cartels, but the changes in the scale and geography of collusion in the European market from the post-war decades until the present have not been systematically investigated. Using network analysis methods and an original dataset based on decisions in EU cartel cases, this paper maps the developments in detected collusion in the European market from 1958 to 2008 and tentatively explains these developments. It appears that collusive activities increased during the 1960s and after the mid-1980s and that a long decline in the scale of collusion began in the mid-1990s. Moreover, the geographical spread of collusive activities in Europe increased considerably from 1969 to 1993. To facilitate an explanation of these and other findings, the paper presents a three-dimensional analytical framework that emphasises the importance of anti-cartel regulation, major changes in the business environment and the size of national economies.