The Norwegian shared library system BIBSYS is in 2010 used by more than hundred university-, college-, and research libraries, including the Norwegian National Library. The BIBSYS project was initiated in 1970 and it led to a complete re-engineering of the Norwegian research libraries. The paper describes the project, how the system was initiated and discusses important decisions made during project development. The two most important factors for the success of BIBSYS are discussed. One is that the project started with a detailed information analysis prior to coding and data base design, using a good software tool. The other factor is that the potential users of the system, the librarians, were included in the project loop from the beginning.