In order to confirm and amplify the evidence of a transmissible agent in human rheumatoid arthritis (RA) tissue reported in mice experiments, data are presented indicating the transmission of the RA agent from this tissue to chicks as well as from chick to chick and by congenital transmission. Chicks hatched from injected embryonated eggs show clearly identifiable redness of the feet, talipes deformities, and dislocation of the hip. Control embryonated eggs hatched normal chicks. Roentgenograms showed developmental defects of the cervical, thoracic, lumbar, and sacral vertebrae. The chick embryo may provide an avenue to further examine the infectious etiology of RA.