This is a detailed introduction to auction theory. It begins with a simple analysis of standard auctions and then uses a strikingly simple general solution of symmetric private values auctions to prove the payoff equivalence of many auction rules. The basic framework is then modified to admit risk aversion, multi-unit and repeated auctions as well as collusion. Then follows an introduction to optimal auctions, with and without stochastic entry, and to common value auctions and the winner's curse problem. The survey closes with a sample of applications, from the regulation of natural monopolies to price competition in oligopoly and the government securities market. Copyright 1996 by Blackwell Publishers Ltd (This abstract was borrowed from another version of this item.)