The ability of storing, managing, and giving access to the huge quantity of data collected by astronomical observatories is one of the major challenges of modern astronomy. At the same time, the growing complexity of data systems implies a change of concepts: the scientist has to manipulate data as well as information. Recent developments of the `WorldWideWeb' bring interesting answers to these problems. The book presents a wide selection of databases, archives, data centers, and information systems. Clear and up-to-date descriptions are included, together with their scientific context and motivations. Audience: This volume provides an essential tool for astronomers, librarians, data specialists and computer engineers.The ability of storing, managing, and giving access to the huge quantity of data collected by astronomical observatories is one of the major challenges of modern astronomy. At the same time, the growing complexity of data systems implies a change of concepts: the scientist has to manipulate data as well as information. Recent developments of the `WorldWideWeb' bring interesting answers to these problems. The book presents a wide selection of databases, archives, data centers, and information systems. Clear and up-to-date descriptions are included, together with their scientific context and motivations. Audience: This volume provides an essential tool for astronomers, librarians, data specialists and computer engineers.1. Facets and Challenges of the Information Technology Evolution; A. Heck. 2. The Compton Gamma-Ray Observatory Archive; P. Barrett. 3. Data from the X-Ray Observatory ROSAT; H.U. Zimmermann, et al. 4. The Einstein On-Line Service; D.E. Harris, C.S. Grant. 5. The EUVE Archive; Center for Extreme Ultraviolet Astrophysics. 6. The IUE Archives; M. Barylak, et al. 7. Building the Archive Facility of the ESO Very Large Telescol#S