This paper develops a theory concerning the centralization degree of firms involving in multimarket collusive agreements. We examine the impact of exogenous organizational structures on collusive strategy. We then go on to consider the endogenous case. A centralized organization (unitary or U-form) allows price coordination on several markets whereas a decentralized one (multidivisional or M-form) decreases the probability that the antitrust authority will find evidence of collusion on one market during an investigation in the other. We show that this trade-o ff depends to a great extent on product substitutability and upon the instruments used by the antitrust authority.