Data from clinical practice is needed to understand the safety, effectiveness, and optimal use of available and emerging treatment options for inﬂammatory arthritis. We have demonstrated the value of our individual registers in assessing the safety and effectiveness of TNF-inhibitors in RA, AS/SpA and PsA. Many outstanding issues, particularly in AS/SpA and PsA, can, however, only be addressed through collaboration across registers. The Nordic countries have similar healthcare systems and other national registers that can be linked together. ARTIS (Sweden), DAN-BIO (Denmark), NOR-DMARD (Norway), ROB-FIN (Finland) and ICEBIO (Iceland) represent some of the largest registers of inﬂammatory arthritis and their therapies.