The polysaccharide-free lipoid A component of E. coli 0111:B4 endotoxin produces hemorrhagic necrosis in sarcoma 180 of mice, but is somewhat less effective than the lipopolysaccharide from which it was derived. A trichloracetic acid extract obtained from S. aureus strain D was slightly more effective than the E. coli lipopolysaccharide on this tumor.