<jats:title>Abstract</jats:title><jats:p>Four linear 20‐residue peptaibols, named metanicins (MTCs) A–D, were isolated from submerged cultures of the ascomycetous fungus CBS 597.80. Structure elucidation was performed by a combination of fast‐atom‐bombardment mass spectrometry (FAB‐MS), electrospray ionization MS, <jats:italic>Edman</jats:italic> degradation of isolated fragments, and amino acid analysis by ion‐exchange and gas chromatography, and enantioselective HPLC. The sequences of MTC A(B) are (amino acid exchange in B and C in parentheses): Ac‐Aib‐Ala‐Aib‐Ala‐Aib‐Ala‐Gln‐Aib‐Val‐Aib‐Gly‐Leu‐Aib‐Pro‐Val‐Aib‐Aib(<jats:sc>D</jats:sc>‐Iva)<jats:italic>‐</jats:italic>Gln‐Gln‐Pheol and of MTC C(D) Ac‐Aib‐Ala‐Aib‐Ala‐Aib‐Ala‐Gln‐Aib‐Val‐Aib‐Gly‐Leu‐Aib‐Pro‐Val‐Aib‐Aib(<jats:sc>D</jats:sc>‐Iva)<jats:italic>‐</jats:italic>Gln‐Gln‐Pheol (Ac, acetyl; Aib, <jats:italic>α</jats:italic>‐aminoisobutyric acid; Iva, isovaline; Pheol, <jats:sc>L</jats:sc>‐phenylalaninol). The peptides are related, and some of the sequences are identical, to other 20‐residue peptaibols isolated from <jats:italic>Trichoderma</jats:italic> species. MTCs show moderate activities against <jats:italic>Micrococcus luteus, Enterococcus faecalis</jats:italic>, and <jats:italic>Staphylococcus aureus</jats:italic>, and very low activities against <jats:italic>Bacillus subtilis.</jats:italic> The producer has originally been identified and deposited as <jats:italic>Metarhizium anisopliae</jats:italic> var. <jats:italic>anisopliae</jats:italic> CBS 597.80. Although this identification has been withdrawn by <jats:italic>Centralbureau voor Schimmelcultures</jats:italic> (CBS) in the meantime, the accession number will be retained – independently from any taxonomic revisions.