The lactococcin B (LnB) is a hydrophobic, positively charged bacteriocin, produced by Lactococcus lactis ssp. cremoris 9B4. It consists of a peptidic chain made up of 47 amino acid residues, and inhibits Lactococcus exclusively. In order to study its biological activity a synthetic lactococcin B (LnBs) was obtained by solid-phase chemical synthesis using a Fmoc strategy. LnBs was shown to be indistinguishable from the natural peptide. In addition, a synthetic (7-47) LnBst analogue was obtained by withdrawal of peptidyl-resin after the 41 cycle of LnBs peptide chain assembly. The synthetic N-terminal truncated (7-47) LnBst analogue was found to be inactive on indicator strains. Our results strongly suggest that the first six N-terminal amino acid residues are involved in the bactericidal activity of LnB.