Antibiotic peptaibols (=peptaibophols) represented by alamethicin1} have received attention in terms of the activity against various microorganisms2) as well as the formation of voltage-gated ion channels in membranes3. They contain an aminoalcohol and a high proportion of a-aminoisobutyric acid (Aib). We previously isolated trichopolyns I and II4) of the same class from a culture broth of Trichoderma polysporum (Link ex Pers.) Rifai (Strain TMI 60146), which have a strong antagonistic inhibition against the growth of Lentinus edodes. Further examination on peptide components produced by T. polysporum has led to the isolation of new peptaibols, trichosporins (TS), having an uncoupling activity similar to that of hypelcins5) in mitochondria of rat livers. In this paper, we wish to report the structural elucidation of these peptides.