This paper develops a model of competitive bidding where the winning bidder's payoff depends on his personal preferences, the preferences of others, and the intrinsic qualities of the object being sold. The model shows that the English (ascending) auction generates higher average prices than the second-price auction. When bidders are risk-neutral, the second-price auction generates higher average prices than the Dutch and first-price auctions. The seller can increase the expected price by providing expert appraisals of the object's quality. The paper reviews existing auction theory, including the independent private values model and the common value model, and introduces a new general auction model. It discusses the strategic equivalence of the Dutch and first-price auctions, the equivalence of the English and second-price auctions under certain conditions, and the Pareto optimality of the outcomes in these auctions. The paper also explores the impact of risk aversion on auction outcomes and the role of information in auctions. The general model allows for statistical dependence among bidders' value estimates and accommodates various auction forms, such as the English, second-price, and Dutch auctions. The paper derives several testable predictions, including the strategic equivalence of the Dutch and first-price auctions, the higher expected prices generated by the English auction compared to the second-price auction, and the optimal policy for the seller to maximize revenue. The paper concludes with a discussion of the current state of auction theory and technical appendices that provide additional mathematical details.This paper develops a model of competitive bidding where the winning bidder's payoff depends on his personal preferences, the preferences of others, and the intrinsic qualities of the object being sold. The model shows that the English (ascending) auction generates higher average prices than the second-price auction. When bidders are risk-neutral, the second-price auction generates higher average prices than the Dutch and first-price auctions. The seller can increase the expected price by providing expert appraisals of the object's quality. The paper reviews existing auction theory, including the independent private values model and the common value model, and introduces a new general auction model. It discusses the strategic equivalence of the Dutch and first-price auctions, the equivalence of the English and second-price auctions under certain conditions, and the Pareto optimality of the outcomes in these auctions. The paper also explores the impact of risk aversion on auction outcomes and the role of information in auctions. The general model allows for statistical dependence among bidders' value estimates and accommodates various auction forms, such as the English, second-price, and Dutch auctions. The paper derives several testable predictions, including the strategic equivalence of the Dutch and first-price auctions, the higher expected prices generated by the English auction compared to the second-price auction, and the optimal policy for the seller to maximize revenue. The paper concludes with a discussion of the current state of auction theory and technical appendices that provide additional mathematical details.