Despite the fact that over half of U.S. residents are now online, Internet users hesitate to enter into transactions with e-retailers in the absence of certain assurances. Recent IS research shows that institution-based assurance structures, such as Web seals, are drivers of online trust. We extend the research in online trust to include the effect of third-party organization (TPO) credibility on both Internet users perceptions of assurance structures and purchase risk. Findings indicate that TPO credibility is positively related to the value that Internet users assign to assurance structures and negatively related to perceptions of purchase risk. Furthermore, perceptions of TPO credibility are strongly associated with users trusting attitudes toward the e-retailer. For some online consumers, trust may have less to do with privacy and security and more to do with the reputation of the TPO. These findings have important implications for the design of Web sites, the selection of assurance providers and services, and the reputation of both e-retailers and providers.