We were approached in December 1998 by one of the founders of Up4Sale, an online auction site that had been purchased a few months earlier by eBay.We were informed that eBay was interested in providing a dispute resolution opportunity for its users and asked whether we would be interested in conducting a pilot project to determine whether mediation could be provided effectively for disputes arising out of auction-related transactions. For a period of about a month in early 1999, information about our service and a link to our complaint form was placed on the Up4Sale site. We received an average of two to four disputes a week during this time and began to understand the types of disputes arising out of auction sites and the types of interactions with parties that might be possible.In late February 1999, we agreed to expand the project to the much larger eBay site.11 Starting in mid-March 1999, a link was placed on the eBay customer service page informing users that they could obtain assistance in transaction-related disputes by clicking on a link to us and filling out a complaint form. EBay did not publicize the link, and the customer service page was two levels down on its site. Even so, during a two week period, 225 buyers and sellers found the link and filed a complaint.To resolve the transaction-related disputes, we decided to use mediation rather than arbitration and a single mediator rather than a group of mediators. We chose mediation largely because we thought it would be easier to obtain the participation of the second party. Online arbitrationprojects such as the Virtual Magistrate project have encountered serious problems obtaining cases because respondents have been unwilling to consent to the decisionmaking authority of the arbitrator.17 In this initial project, we expected no difficulty in obtaining disputes, but we felt that one lesson of online ADR had been that mediation was more likely to be acceptable toparties than arbitration.