We have developed sensitive and specific solid-phase radioimmunoassays to quantitate the distribution and persistence of bacterial antigen in rats developing arthritis in response to a single injection of streptococcal cell wall material. Three separate assays were specific for either the A polysaccharide (N-acetyl-D-glucosamine), A-variant polysaccharide (polyrhamnose), or peptidoglycan (D-ala-D-ala) moieties of the streptococcal cell wall. Antigen was detected in all tissues surveyed, although the greatest amount was in the liver and spleen. By using three fractions of cell wall separated by size, we have shown that the development of arthritis correlates with the degree of cell wall deposited and persisting in the joints. Further statistical analyses suggested differences in metabolism by different tissues and differential metabolism of different antigenic epitopes in some cases.