The results presented indicate that substances with different activities on E. coli are present in exudate produced in rats during the later stages of intestinal strangulation obstruction. The sterile filtered exudate contains substances which inhibit the bactericidal activity of normal serum on the bacteria. These substances do not appear to be adsorbed to the bacteria. Other substances in the filtrate stimulate the deleterious effect of serum on E. coli. These substances are probably adsorbed to the bacteria.