IN the course of extraction of highly polymerized bacterial deoxyribonucleic acid from Brucella abortus cells first killed with 0.5 per cent phenol and then exposed to sodium deoxycholate, it was discovered that phenol treatment alone results in the recovery of material high in content of deoxyribonucleic acid. The acid isolated by this phenol procedure proved to possess specific transforming activity. Its breakdown products exerted selective effects upon bacterial population changes1,2 ; they also reduced the LD50 of pneumococci for mice2 and enhanced phagocytosis in vitro (Pomales-Lebron, A., Braun, W., and Stinebring, W., unpublished results); they also stimulated the growth of lymphosarcoma cells in mice. The polymerized material produced antibodies that appear to show a specificity for the deoxyribonucleic acid molecule3. In view of these diverse biological effects, additional details regarding the phenol extraction procedure and some characteristics of the resulting material will be presented here.