Online reverse auctions are a relatively new phenomenon in business, although the practice of traditional auctions is centuries old. The online aspect of auctions is an example of a disruptive technology and its impact on the business world. The use of the internet has changed the face of competition in supply and also changed the way buyers and suppliers interact. This chapter is a topological classification of the current literature on e-procurement auctions with the intent of organizing current and future research in online procurement auctions.. Over 200 articles have been abstracted and reviewed. The authors develop three classification frames: content, theory, and methodology. Nineteen content areas are populated, including significant reference to the impact of auctions on the supply chain. In summary, this chapter seeks to increase the topic clarity of current research. The quality of each individual reverse auction paper is not evaluated. However, the classification should stimulate academics to pursue current and new avenues of reverse auction research.