RABBIT is the German register for the long-term observation of therapy with biologics in adult patients with rheumatoid arthritis. In May 2001, the project was established in coordination with the German Society of Rheumatology (Deutsche Gesellschaft für Rheumatologie), the Professional Association of Rheumatologists (Berufsverband Deutscher Rheumatologen), and the Competence Network Rheumatology (Kompetenznetz Rheuma). RABBIT is included in the international research network of the European biologics registers.