This handbook is a guide to the library database system Allegro, used for cataloguing in many small and medium sized special libraries (with up to about 100,000 volumes). Students of librarianship also use it during their education. This handbook offers a practice-based guide to cataloguing with Allegro and is a textbook and reference work for both beginners and experienced users. It is relevant to countries where the RAK-WB cataloguing system is in use (Austria, East Belgium, Germany and Switzerland).