The ability of an incumbent firm to deter entry by writing exclusionary contracts with customers has been a subject of contention in the antitrust literature. The courts' concern with such exclusionary contracts has been challenged by those who argue that an incumbent, faced with buyers whose interest is to promote entry and competition, would have to pay buyers more for the inclusion of exclusionary provisions than it could possibly gain from exclusion. In a provocative article, Eric B.

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... n et al. (1991) (henceforth, RRW) have argued that an incumbent may in fact be able to exclude rivals profitably using such contractual provisions because it can exploit buyers' lack of coordination. In essence, if buyers expect other buyers to sign such provisions, then they may see little reason not to do so themselves. The RRW argument is potentially an important one because most alleged instances of entry deterrence through exclusionary contracts with customers occur in situations with multiple buyers. 1,2 Unfortunately, however, RRW's two main results contain errors. In this Note, we reconsider the RRW model, providing correct characterizations of the likelihood and cost of exclusion for an incumbent firm. Our results indicate that while the intuition suggested by RRW is valid, the equilibrium likelihood and cost of exclusion differ from what RRW derive. Moreover, our analysis illuminates some further aspects of exclusionary contracting with multiple buyers. Among these issues, we focus on how an incumbent can use discriminatory offers to exploit the externalities that exist among buyers in the provision of competition. 3 In Section I, we review the basic assumptions of the RRW model. In Sections II and III we then consider, in turn, the cases of simultaneous and sequential offers studied by RRW. For the simultaneous model, we distinguish between settings in which the incumbent can and cannot discriminate in its offers to different buyers. (This distinction is the source of the problem in RRW's analysis: their simultaneous-offer model assumes no discrimination, but the proof of their Proposition 2 assumes-at times-that discrimination is feasible.) We show that absent the ability to discriminate, the incumbent can exclude profitably only when buyers fail to coordinate on their most preferred continuation equilibrium. In contrast, we show that when discrimination is possible, the incumbent need not rely on a lack of buyer coordination to