Native mouse type II collagen was used for immunization of DBA/1 mice. Arthritis developed exclusively in male animals and was characterized by a variable and delayed onset, a slow and progressive development, and frequent exacerbations of disease in several joints including those that were previously affected. Titers of anti-type II collagen autoantibodies were found not to correlate well with arthritis development. It appears that experimental arthritis induced with homologous type II collagen resembles rheumatoid arthritis in humans, both in certain clinical features and in the lack of correspondence between anti-type II collagen autoantibody titers and disease symptoms.