Since the 1990s, there has been a major renewal into research on cartels. One essential question triggered by this recent research is: are international cartels more effective than national ones? There are three possible entry points: to study cartels (including international cartels) as institutions; to analyze cartel behavior, as currently done in the American, German or French-speaking historiography; third, to take an interest in cartel actors, especially the decision-makers, politicians, businessmen, and companies. This third approach was chosen to study the European cement oligopoly. Analysing the archives and internal sources of the cement groups and their banks (the Banque de Paris et des Pays-Bas, Crédit Lyonnais) throws light on the relationships between the members of the cement oligopoly, the constitution of temporary agreements and creation of cartels, the paper examines the case of Lafarge, Italcementi, Buzzi Unicem, Cemex, Dyckerhoff, Heidelberg Cement, Vicat and, above all Holcim (former Holderbank). Three epochs emerge from our study: the formation of national oligopolies, from the 1880s to the late 1940s; the creation of a world-dominant European oligopoly from the early 1950s to the 1990s; and finally the questioning of the European oligopoly, from the 1990s and, especially, 2000s.