Three different tests were performed to investigate the effect of teicoplanin on lipopolysaccharide (LPS). After incubation for 3 h with teicoplanin, LPS from Salmonella minnesota R595 showed reduced reactivity in the metachromatic dimethyl-methylene blue assay and the limulus amoebocyte lysate test. In addition, galactosamine-sensitized mice had an increased survival rate, from 29% to 72%, when teicoplanin was pre-incubated for 3 h with the LPS to be injected intraperitoneally. The results suggest that teicoplanin may have a neutralizing effect on LPS.