Among 170 streptococcal strains, there were encountered 98 that yielded culture supernates which caused splitting of diphosphopyridine nucleotide (DPN). All of the latter belonged to Group A, C, or G. Release of DPNase accompanied the growth of diverse antigenic types of Group A streptococci, and data on the frequency of DPNase-producing strains for certain types are given. In contrast, cultures representing 3 species of yeasts and 42 species of bacteria other than streptococci of the Lancefield groups were examined for the presence of DPNase as an extracellular product of growth, but in none of these was the enzyme detected.

Of the Group A streptococci examined, 41 strains had pedigrees suggesting that they were the etiologic agents of acute glomerulonephritis, and 39 of these were found to produce DPNase.

There is an association between capacity of streptococi to form DPNase and capacity to kill leukocytes. A possible mechanism of leukotoxicity is suggested.