This article describes the development and empirical status of guided Internet-delivered self-help. The treatment approach combines the benefits of bibliotherapy with book-length text materials and the support given online via web pages and e-mail. Interactive features such as online registrations, tests, and online discussion forums are also included. Cognitive behavior therapy (CBT) guided the research and clinical implementations of this approach, as it lends itself more easily to the self-help format compared with other presently available psychotherapy approaches. We include an overview of the research, current issues and research in service delivery, lessons learned through a program of research, and directions for future investigations.