WebQual is an instrument for assessing the quality of Internet sites from the perspective of the customer. Earlier versions of WebQual focused on information and interaction quality. This paper reports on a new version of WebQual that incorporates three quality dimensions: information quality, interaction quality and Web site design quality. WebQual is applied in the domain of Internet auctions and the results are used to assess the reliability of the instrument for assessing the quality of Web sites. Three auction sites (Amazon, eBay and QXL) are evaluated through an intervention that involves buying and selling at auction. The results of the intervention are analyzed quantitatively to assess the validity of the WebQual instrument and supplemented by qualitative data that is used to consider the relative merits of the three sites evaluated.