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This paper studies federal auctions for wildcat leases on the Outer Continental Shelf from 1959 to 1970. These are leases where bidders privately acquire (at some cost) noisy, but equally informative signals about the amount of oil and gas that may be present. We develop a test of equilibrium bidding in a common values model that is implemented using data on bids and ex post values. We compute bid markups and rents under the alternative hypotheses of private and common values and find that the data are more consistent with the latter hypothesis. Finally, we use data on tract location and ex post values to test the comparative static predicton in common value auctions that bidders tend to bid less aggressively when they expect more competition. *Hendricks and Pinkse: Department of Economics, University of British Columbia, Vancouver, BC, Canada V6T 1Z1. Porter: Department of Economics, Northwestern University, Evanston, IL 60208. We received helpful comments from Susan Athey, Phil Haile, Preston McAfee and from the participants in a number of seminars. Hendricks and Pinkse received financial support from SSHRCC, and Porter from the NSF.