Serological analysis of the sera produced by injection of chondromucoprotein from various species cross reacted. There were species-specific and non-species-specific determinants. The former had much higher titer than the latter. Rabbit antisera to guinea pig chondromucoprotein with titers over 1:8,000 on hemagglutination test were pooled and the immune globulin fraction prepared, after inactivation and absorption of non-tissue-specific antibodies. Repeated intra-articular injection of this immune globulin into young adult guinea pigs caused an arthritis similar to human osteoarthritis, indicated by histochemical and autoradiographic studies.