This chapter introduces the trust virtual organization as a means of facilitating authentication and authorization for sharing distributed and protected contents and services. It indicates that sharing institutional protected services and deliverables has proven a hurdle since user accounts are created in many sites. It provides an approach to solving this problem using virtual organizations with cross-institutional Single Sign On, with which users use their existing institutional accounts to login. This chapter also presents the challenges of building trust virtual organizations: managing users from distributed identity providers; managing services from distributed services providers; managing trust relationships between users and services, and authorizing the access privileges to users based on the trust relationships. It argues that the trust virtual organization increase the effectiveness of e-learning, e-research and e-business significantly. Furthermore, the authors hope that the trust virtual organization facilitates not only Web-based authentication and authorization, but also grid-based authentication and authorization.