The paper discusses the critical issues in auction design, emphasizing the traditional concerns of competition policy—preventing collusive, predatory, and entry-deterring behavior. Ascending and uniform-price auctions are particularly vulnerable to these problems, while the Anglo-Dutch auction, a hybrid of sealed-bid and ascending auctions, may often perform better. Effective anti-trust policy is also crucial. The design of auctions depends heavily on the context, as illustrated by the contrasting outcomes of the U.K. and Dutch 3G spectrum auctions. The paper also addresses other issues such as political problems, the need for clear and credible rules, and the importance of reserve prices. It concludes that auction design is most effective when dealing with monopsony and oligopsony power, and suggests the Anglo-Dutch auction as a solution to the limitations of ascending auctions.The paper discusses the critical issues in auction design, emphasizing the traditional concerns of competition policy—preventing collusive, predatory, and entry-deterring behavior. Ascending and uniform-price auctions are particularly vulnerable to these problems, while the Anglo-Dutch auction, a hybrid of sealed-bid and ascending auctions, may often perform better. Effective anti-trust policy is also crucial. The design of auctions depends heavily on the context, as illustrated by the contrasting outcomes of the U.K. and Dutch 3G spectrum auctions. The paper also addresses other issues such as political problems, the need for clear and credible rules, and the importance of reserve prices. It concludes that auction design is most effective when dealing with monopsony and oligopsony power, and suggests the Anglo-Dutch auction as a solution to the limitations of ascending auctions.