The viability of Enterobacter agglomerans, a common gram-negative bacterium in cotton dust, was significantly reduced by a 100,000 X G ovine surfactant fraction and compliment-inactivated serum combination. Surfactant alone did not kill the bacterium. However, it greatly enhanced the bacterial mortality observed with serum. Lipopolysaccharide (LPS) preincubated with the surfactant fraction inhibited the synergistic effect of surfactant. Serum lipids, but not ovine albumin, proved bactericidal. E. agglomerans LPS did not inhibit the bactericidal effect of the serum lipids. The data indicates that LPS complexes with a surfactant fraction constituent responsible for enhancing the bactericidal capability of serum.