Immunization of DBA/1 mice with native chick type II collagen resulted in development of polyarthritis 4-5 wk later. Sera of these mice contained high levels of anticollagen antibodies, and immunoglobulin concentrates of their sera transferred arthritis to unimmunized recipients. Histopathologically, this passively transferred arthritis resembled the early disease of immunized donors. Immunofluorescence studies demonstrated the deposition of IgG and C3 on the articular surface but not in synovial tissue of arthritic joints. Transferred, isotopically labeled anticollagen antibodies rapidly localized to the limbs and to other cartilage-containing tissues. When transfer concentrate was administered to arthritis-resistant strains, they also developed arthritis. Indeed, immunoglobulin concentrates from rats with collagen-induced arthritis transferred arthritis to naive mice. The amount of concentrate required for transfer to B10.D2 resistant mice was reduced by immunizing them with collagen 4 wk before transfer. Although susceptibility to arthritis from immunization is H-2 linked, these studies clearly demonstrate that passive transfer of arthritis depends upon injection of specific antibody and not on other host factors.