Abstract: This talk is concerned with identification of the distribution of bidder valuations in some incomplete models of open outcry ascending English auctions. Results from Chesher and Rosen (Ecta, 2017) are summarized and deployed to characterize identified sets for bidder valuation distributions and functionals of these distributions. The analysis is relevant to demand estimation because the survivor function of the distribution of valuations is the bidders' demand schedule. English auction data deliver bounds on valuations. It is shown how this leads to sharp bounds on the valuation distribution improving on the Haile and Tamer (JPE, 2003) bounds. Models admitting observed and unobserved auction-specific heterogeneity are considered and bounds on the impact on the valuation distribution of the characteristics of the auctioned item are derived.