This paper considers the problem of designing selling procedures for substitutes (like condominium units). Oral ascending auctions for the right to choose are efficient. This is a common type of auction used for the sale of real estate. Efficiency is not optimal from the seller's viewpoint. An optimal procedure distorts the right-to-choose auction to favor in late rounds bidders whose preferred object has already been sold. This optimal auction is complex. A revenue improving departure from efficiency can be achieved by simply auctioning all the rights to choose before any of them is exerted. © Springer-Verlag 2005.

Financial aid from the European Commission through the TMR Program (contract FMRX-CT98-0203) and the SpanishMCyT(Grants SEC 2002-02506 and SEC 2003-08080) is gratefully acknowledged.

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