The authors consider auctions for a single indivisible object when bidders have information about each other that is unavailable to the seller. They show that the seller can use this information to his own benefit, and they characterize th e environments in which a well-chosen auction gives him the same expected payoff as that obtainable were he able to see the object und er full information. This hinges on the possibility of constructing lotteries with the correct properties. The authors study the problem for auctions where the bidders have dominant strategies and those where the relevant equilibrium concept is Bayesian-Nash. Copyright 1988 by The Econometric Society.

[This paper deals with the optimal design of resource allocation mechanisms in the presence of asymmetric information. A buyer's valuation function is allowed to depend on the characteristics of other buyers as well as his own and sufficient conditions are provided under which the seller can extract the full surplus from the buyers in an "ex post Nash" equilibrium. The result is then applied to the important problem of optimal auction design.]