The studies presented in the foregoing paper are reviewed at this time as matters of observation only. A discussion of the interpretation and possible significance of the results will be found in the following communication. It has been shown that, in the majority of cases, the sera of patients with rheumatoid arthritis possess the property of agglutinating strains of Streptococcus hemolyticus (at 55°C.) to an extraordinarily high titer. No correlation was observed between the source of the strains and their agglutinability in the sera examined. Strains of Streptococcus hemolyticus obtained from cases of scarlet fever, erysipelas and rheumatic fever were agglutinated to as high a titer as were the “typical strains” of Cecil, Nicholls and Stainsby. Agglutination tests with a wide variety of other Gram-positive cocci revealed that these organisms were either not agglutinated at all or were agglutinated to a very low titer. An exception to this generalization is made in the case of R pneumococci which were agglutinated to almost as high a titer as were strains of Streptococcus hemolyticus. With the exception of certain instances, which are referred to in some detail, control sera did not agglutinate strains of Streptococcus hemolyticus in a titer which was comparable with that observed in rheumatoid arthritis.