Collusive practices attract much attention from the public, the press, and governments, especially when the interests of consumers are at stake. In the perception of society the varieties of collusion are surrounded by an air of secretiveness and the excessive earnings of managers. Collusion among businessmen is, however, as old as the hills. Since the late nineteenth century a wide variety of collusive practices occurred, ranging from business interest associations and cartels, to full mergers and acquisitions. Literature on corporatism, institutional economics, industrial organization, and also business history pays a lot of attention to the various types of collusion and concentration. However, much less is known about the development in use and perception of each of these collusive practices and the interaction among various forms of cooperation among businessmen. What is the coherence and relation between the activities of business interest associations, the existence of cartels and the occurrence of mergers and acquisitions? Can we distinguish a sequence of collusive practices and how do these different forms of collusion interact? This paper explores this somewhat neglected issue and looks at both the economic and institutional dynamics of collusion. It focuses on the long-term development and fashions in the concentration process that shaped market structures. We distinguish three different forms of collusion: business interest associations, cartels, and mergers, and acquisitions. They representdifferent degrees of concentration, but in our opinion they should not be seen as separate phenomena.