Animal models are instrumental in understanding the etiology and pathogenetic mechanisms of rheumatoid arthritis. Several new mouse models have either been produced, including transgenics, gene-knockouts, and gene knock-ins, or established as a spontaneous disease due to natural gene mutations. These models are suitable for addressing the roles of T cells, autoantibodies, cytokines and innate immunity in the development and progression of rheumatoid arthritis. In particular, they now provide insights into how systemic alterations of the immune system result in a local development of chronic arthritis that leads to joint destruction.