The full-length cDNA of a neutrophil antibiotic dodecapeptide has been cloned by reverse transcription/PCR from bovine bone marrow RNA. This peptide was originally isolated from bovine neutrophils, and shown to exert a potent antimicrobial activity in vitro on both Escherichia coli and Staphylococcus aureus. The cDNA codes for a polypeptide of 155 amino acid residues with a predicted mass of 17,629 Da and a pI of 8.03. The deduced sequence comprises a putative signal peptide of 29 amino acids, a 114 residue pro-region, and a carboxy-terminal dodecapeptide corresponding to the mature antibiotic. The pro-sequence displays extensive identity to corresponding regions of other structurally unrelated antibiotic peptides of bovine neutrophils recently cloned.