Seven strictly anaerobic strains showing anti-Salmonella enteritidis activity were isolated from poultry caecal contents. Among them, the most inhibitory one, a strain of Fusobacterium mortiferum, called FM1025, was selected. Biochemical tests, showing the proteinaceous structure of the antagonist(s) produced, indicated that the strain Fus. mortiferum FM1025 synthesized (a) bacteriocin-like compound(s) active against Salm. enteritidis. Among the other strains tested, both Gram-negative and Gram-positive bacteria were inhibited. These preliminary results suggested the important role of the Fusobacterium strains against pathogenic bacteria among the intestinal flora.