Recent observations on streptococcal antihyaluronidase in human sera have shown that the concentration of that antibody is elevated above the normal in acute rheumatic and streptococcal infection. Within the clinical groups mentioned it has been found that the mean antihyaluronidase titer is higher in acute rheumatic fever than following streptococcal infections, and that the range of such titers in the former disease extends above the range found in the latter.1, 2, 3, 4These observations have directed interest to the question of antibody levels to this streptococcal enzyme in two other diseases: glomerulonephritis, because of its similarity to rheumatic fever...