This paper characterizes the optimal selling mechanism in the presence of horizontal
crossholdings. We find that this mechanism imposes a discrimination policy against the
stronger bidders so that the seller´s expected revenue is increasing in both the
common crossholding and the degree of asymmetry in crossholdings. Furthermore, it
can be implemented by a sequential procedure that includes a price-preferences
scheme and the possibility of an exclusive deal with the weakest bidder. We also show
that a simple sequential negotiation mechanism, although suboptimal, yields a larger
seller´s expected revenue than both the first-price and the second-price auctions