Bacillomycin D is an antifungal agent extracted from the culture medium of a strain of Bacillus subtilis. It is a mixture of two homologous lipopeptides: the lipid moiety consists of 3-amino-12-methyltridecanoic acid or 3-amino-12-methyltetradecanoic acid; the peptide moiety contains one residue of each of the following seven amino acid: D-asparagine, L-aspartate, L-glutamate, L-proline, D-serine, L-threonine and D- tyrosine. The peptide sequence and the cyclic structure were determined by structural analysis of the peptides obtained by mild acid hydrolysis and by cleavage of the molecule with N-bromosuccinimide.