New membrane-modifying peptides, trichorozins I-IV, have been isolated from conidia of the fungus Trichodermaharzianum. Their amino acid sequences were clearly determined by spectrometric methods and, furthermore, they were synthesized by the solution-phase method. Trichorozins are a family of the class of peptaibols and are composed of 11 residues including an amino alcohol. Trichorozins exhibited